I've had some reports of issues after updating to El Capitan. I haven't updated yet myself - it might be a little bit before I can, and before I can really get into these issues.
Since you haven't updated yet though, I doubt that that is the issue here. I'm not sure what is causing the problems, but if the problem persists you could try removing the preferences for those characters, which should cause Avalon to create fresh new files for them.
To do that, while Avalon is not running, go to your user directory -> Applications -> Simutronics -> GS, and just move try moving a directory that's named the same as one of the characters in question out of there (to, say, your desktop). The next time that you start Avalon and login with that character it should create a fresh set of files. You'll have to redo the window positions and such, but hopefully that will stop it from re-occurring.
As a second step, you should be able to duplicate a directory for a character that's setup how you want and working well, and rename it to another character, and copy those settings over to that character without having to redo them all.
Hopefully that will work out. Sometimes weird things happen with the prefs though :(
Ixix
