Opponents Unmasking Counters

Model Dell XPS 8900
Operating System - Windows 10 Home
CPU - i7 6700
Memory - 32 GB
Video Card NVidia GeForce GTX 745
Vassal version - 3.2.16
Java version - 1.8.0_91-b14
Vassal module name and version - Tunisia II 1.0

Masking is enabled for most of the counters in the module and controlled by specifying which sides can mask a particular counter.

In Global Options, the ‘Allow non-owners to unmask pieces’ is set to ‘User Preference Settings’

In preferences, both players have checked the ‘Opponents can unmask my pieces’ option.

However, when one side masks a counter, saves the vlog/vsav file, and then sends it to his opponent,
the opponent has been unable to unmask the counter (the shortcut option does not appear when they right-click the counter).

If I change the ‘Allow non-owners to unmask pieces’ Global Option to ‘Always’ it doesn’t appear to work either.

Any ideas what is preventing the players from unmasking?