It is 3 back-ticks (not regular apostrophe) that you need to put before and after quoting the errorLog - see also How to format forum posts. The three ``` before and after makes the text come out unformatted and in an monospace font - making it much easier to digest. See below
As far as I can see, you have 3 starts of Vassal in the above.
First one
with the module C:\\Users\\DSuls\\Downloads\\GTC2_3_04.vmod and save file C:\\Users\\DSuls\\OneDrive\\Desktop\\Vassal Games\\turn3_union_activation_next.vsav
2026-08-11 12:26:26,605 \[17764-main\] INFO VASSAL.launch.StartUp - Starting
2026-08-11 12:26:26,626 \[17764-main\] INFO VASSAL.launch.StartUp - OS Windows 11 10.0 amd64
2026-08-11 12:26:26,626 \[17764-main\] INFO VASSAL.launch.StartUp - Java version 26.0.1
2026-08-11 12:26:26,626 \[17764-main\] INFO VASSAL.launch.StartUp - Java home C:\\Program Files\\VASSAL-3.7.26\\jre
2026-08-11 12:26:26,627 \[17764-main\] INFO VASSAL.launch.StartUp - VASSAL version 3.7.26
2026-08-11 12:26:26,724 \[17764-AWT-EventQueue-0\] INFO VASSAL.launch.ModuleManager - Manager
2026-08-11 12:35:05,057 \[17764-SwingWorker-pool-2-thread-1\] INFO VASSAL.launch.AbstractLaunchAction - Loading module file C:\\Users\\DSuls\\Downloads\\GTC2_3_04.vmod
2026-08-11 12:35:06,835 \[17764-SwingWorker-pool-2-thread-1\] INFO VASSAL.launch.TilingHandler - No images to tile.
2026-08-11 12:35:06,835 \[17764-SwingWorker-pool-2-thread-1\] INFO VASSAL.launch.AbstractLaunchAction - Loading game file C:\\Users\\DSuls\\OneDrive\\Desktop\\Vassal Games\\turn3_union_activation_next.vsav
2026-08-11 12:35:06,835 \[17764-SwingWorker-pool-2-thread-1\] INFO VASSAL.launch.AbstractLaunchAction - Loading module Grant Takes Command II
2026-08-11 12:35:06,835 \[17764-SwingWorker-pool-2-thread-1\] INFO VASSAL.launch.AbstractLaunchAction - JVM maximum heap size: 1024 MB
2026-08-11 12:35:06,845 \[17764-SwingWorker-pool-2-thread-1\] INFO VASSAL.tools.io.ProcessLauncher - launching C:\\Program Files\\VASSAL-3.7.26\\jre\\bin\\java -Xms1024M -Xmx1024M -Duser.home=C:\\Users\\DSuls -Duser.dir=C:\\Program Files\\VASSAL-3.7.26 -cp lib\\Vengine.jar VASSAL.launch.Player --load – C:\\Users\\DSuls\\Downloads\\GTC2_3_04.vmod C:\\Users\\DSuls\\OneDrive\\Desktop\\Vassal Games\\turn3_union_activation_next.vsav
2026-08-11 12:35:07,384 \[9896-main\] INFO VASSAL.launch.StartUp - Starting
2026-08-11 12:35:07,394 \[9896-main\] INFO VASSAL.launch.StartUp - OS Windows 11 10.0 amd64
2026-08-11 12:35:07,394 \[9896-main\] INFO VASSAL.launch.StartUp - Java version 26.0.1
2026-08-11 12:35:07,394 \[9896-main\] INFO VASSAL.launch.StartUp - Java home C:\\Program Files\\VASSAL-3.7.26\\jre
2026-08-11 12:35:07,394 \[9896-main\] INFO VASSAL.launch.StartUp - VASSAL version 3.7.26
2026-08-11 12:35:07,394 \[9896-main\] INFO VASSAL.launch.Launcher - Player
2026-08-11 12:35:10,237 \[9896-AWT-EventQueue-0\] INFO VASSAL.build.GameModule - Grant Takes Command II version 3.04
Second one
with module C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod and no save file
2026-08-11 14:53:08,804 \[17764-SwingWorker-pool-2-thread-2\] INFO VASSAL.launch.AbstractLaunchAction - Loading module file C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod
2026-08-11 14:53:09,284 \[17764-SwingWorker-pool-2-thread-2\] INFO VASSAL.tools.io.ProcessLauncher - launching C:\\Program Files\\VASSAL-3.7.26\\jre\\bin\\java -classpath lib\\Vengine.jar -Xmx410M -Duser.home=C:\\Users\\DSuls VASSAL.tools.image.tilecache.ZipFileImageTiler C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod C:\\Users\\DSuls\\AppData\\Local\\VASSAL\\tiles\\773689701275239c7a3b0455a843934ed5bd1589 256 256
2026-08-11 14:53:09,662 \[3928-main\] INFO VASSAL.tools.image.tilecache.ZipFileImageTiler - Starting
2026-08-11 14:53:09,706 \[3928-main\] INFO VASSAL.tools.image.tilecache.FileArchiveImageTiler - Tiling images/6MAP-60-1-1.jpg, heap size is 23
...
2026-08-11 14:53:33,756 \[3928-main\] INFO VASSAL.tools.image.tilecache.ZipFileImageTiler - Exiting
2026-08-11 14:53:33,800 \[17764-SwingWorker-pool-2-thread-2\] INFO VASSAL.launch.AbstractLaunchAction - Loading module Grant Takes Command II
2026-08-11 14:53:33,802 \[17764-SwingWorker-pool-2-thread-2\] INFO VASSAL.launch.AbstractLaunchAction - JVM maximum heap size: 1024 MB
2026-08-11 14:53:33,802 \[17764-SwingWorker-pool-2-thread-2\] INFO VASSAL.tools.io.ProcessLauncher - launching C:\\Program Files\\VASSAL-3.7.26\\jre\\bin\\java -Xms1024M -Xmx1024M -Duser.home=C:\\Users\\DSuls -Duser.dir=C:\\Program Files\\VASSAL-3.7.26 -cp lib\\Vengine.jar VASSAL.launch.Player --load – C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod
2026-08-11 14:53:34,334 \[11848-main\] INFO VASSAL.launch.StartUp - Starting
2026-08-11 14:53:34,344 \[11848-main\] INFO VASSAL.launch.StartUp - OS Windows 11 10.0 amd64
2026-08-11 14:53:34,344 \[11848-main\] INFO VASSAL.launch.StartUp - Java version 26.0.1
2026-08-11 14:53:34,344 \[11848-main\] INFO VASSAL.launch.StartUp - Java home C:\\Program Files\\VASSAL-3.7.26\\jre
2026-08-11 14:53:34,344 \[11848-main\] INFO VASSAL.launch.StartUp - VASSAL version 3.7.26
2026-08-11 14:53:34,344 \[11848-main\] INFO VASSAL.launch.Launcher - Player
2026-08-11 14:53:36,890 \[11848-AWT-EventQueue-0\] INFO VASSAL.build.GameModule - Grant Takes Command II version 3.12.0
Note that tiles of images are placed in C:\\Users\\DSuls\\AppData\\Local\\VASSAL\\tiles\\773689701275239c7a3b0455a843934ed5bd1589
Third one
with module C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod again, and no save file
2026-08-11 14:54:35,147 \[17764-SwingWorker-pool-2-thread-3\] INFO VASSAL.launch.AbstractLaunchAction - Loading module file C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod
2026-08-11 14:54:35,526 \[17764-SwingWorker-pool-2-thread-3\] INFO VASSAL.tools.io.ProcessLauncher - launching C:\\Program Files\\VASSAL-3.7.26\\jre\\bin\\java -classpath lib\\Vengine.jar -Xmx410M -Duser.home=C:\\Users\\DSuls VASSAL.tools.image.tilecache.ZipFileImageTiler C:\\Users\\DSuls\\Downloads\\GTC2_3_12.vmod C:\\Users\\DSuls\\AppData\\Local\\VASSAL\\tiles\\773689701275239c7a3b0455a843934ed5bd1589 256 256
2026-08-11 14:54:35,911 \[3484-main\] INFO VASSAL.tools.image.tilecache.ZipFileImageTiler - Starting
...
2026-08-11 14:54:46,833 \[3484-main\] INFO VASSAL.tools.image.tilecache.FileArchiveImageTiler - Tiled images/6MAP-60-4-2.jpg, heap size is 401
2026-08-11 14:54:46,833 \[3484-main\] INFO VASSAL.tools.image.tilecache.FileArchiveImageTiler
Again, the tiles are made in C:\\Users\\DSuls\\AppData\\Local\\VASSAL\\tiles\\773689701275239c7a3b0455a843934ed5bd1589. That’s a bit strange - the first run should have made all the tiles and there should be no need to create the tiles again.
Other than that, there’s nothing in the log that is suspicious. However, the log is cut off in the bottom, so there might be more.
I just tried the 3.12.0 module from On to Richmond II: The Union Strikes South, by opening up the module, select the scenario GTC N, then save. Then I quit the module, and then open the save file. Everything seems to work fine. This is with Vassal 3.7.26 on Linux and Java 27-ea (early access).
Perhaps you can try to first delete your errorLog file, and then re-create the problem that you see. Then, the new errorLog should only contain stuff from the failing run. There might be nothing there, so perhaps you could also note down the times where things happened that you observe - so as to correlate it with the log.
Yours,
Christian