Yeah I knew when I reported it, it would be an issue as it was only happening sporadically for us as well! This has since not been an issue and I think I know why. At the time I had created my own copies of the 5e mm basic creatures so that I could update them with an icon instead of the letter in a circle. These entries in the NPC records had no "accompanying module" so I could not share them with the player and they were bugging out and kicking up some errors for him, very hit or miss as well. I am guessing it had something to do with that, as when I realize/believed it was an issue with the npc records, I had him only use official records (not just copies with new icons) and he stopped having both issues. As of today I retested this trying to get the error on the basic mm records and I could not. So it is working as intended. Sorry for the delay in getting back to you on this, I just saw your reply yesterday as I am not on these forms much and researching for a move to FGU.
As for current extensions in FGC, I am only using your druid shapes ext, Player Agency and 5e random treasure generator. (I'm expecting to only use agency and Druid Shape in FGU if possible once we move over).
Level of the single druid at the time of the issues was lvl 2 and lvl 3, in a 5 player game. It was happening more than once, was a problem with the brown or black bear form if I remember, when he would revert his green aura under is player token would remain 2x2 even though the icon was 1 square. Other token's position did not seem to matter, no one was on him and it was happening even when he was solo on a testing map, though there was the whole group in the combat tracker.
Single layer map. Combat rounds on the tracker ? I forget but was most likely less than 10-12 based on what they had done to that point following their last rest. He was in and out of giant spider and bear forms during about 4 sessions with maybe a long and a short rest. During this time my extensions did not change.
Hope this helps if you want to follow it up, but as I said it seems corrected and no longer an issue.
Thanks again for all your work. This extension is really amazing and making our game really fantastic in the ease and control the player has over himself. So we definitely owe you a few rounds if you ever find yourself downunder in Brisbane after travel bans are finished and it's safe once again. Cheers.