Do you have any off-the-top-of your head idea while Vassal would continue to tile images even though no new changes have been made to the module?
There was a bug where timestamps were not saved in the zip properly, which meant the tile cache was rebuilt every time the module was opened. I think you can fix it by just opening the module in edit mode and saving it again, as long as you have a new enough Vassal version.
Sounds reasonable. I’ll do some testing.