No idea what is going on with this. I don't remember what version I had previously as it had been several years since I last played but I don't remember running into this before.
I'm trying to recreate this bug, but have been unable to do so. Did you use the Party Switch menu option from an old save file from a previous version? Or were you playing the story and the party change was forced as part of the plot? If you're using an older save and updated the game, it's possibly a compatibility issue. You can always upload and link your save file prior to the change, and I can try to duplicate the bug with it on the current version.
There is a mechanic that updates player levels so that heroes not in the party don't fall behind in experience gains. The calculations and implementation only occur on party switch. It's also dependent on specific variables that have been tracking total hero levels the entire game (recall you can rebirth a hero to restart at level 1 with current stats intact). If that data is missing, the mechanic could malfunction.
Ugggg....sorry, apparently I didn't set it to notify me on replies. Yes it was with a save from an older version, from before the option to disable exp scaling existed.
But I did figure out how to replicate it, if I talk to the reset NPC (standing infront of him in the save) and try to rebirth and get the "not high enough level" message, then try to change party it will set everyone to 99.
https://drive.google.com/file/d/1ch0qz1PDtOcoQOvtSY4Z4Mp1NNNanGIs/view?usp=drive...
Ok, it took me awhile, but I think I finally figured out the issue. It's not a bug, the programming is functioning as intended. It's as I guessed, the older save file was lacking some initialization data.
Sammy is special and is the only hero that starts with dual wielding weapons. There is code that tracks this in newer versions so the player can change that setting for all heroes once reborn at level 99. Without the trackers initialized, his class was getting reset to the wrong version that has a different experience curve, thus massively boosting his experience level when the code tries to reset hero statistics.
I have uploaded a new version of your save02.lsd file replacing it on your drive that should have the necessary changes to the tracking variables so everything should work correctly. Or you can just continue playing and don't interact with this particular recruitable NPC (Master Miyagi) until every party member is level 99, and then the issue would be irrelevant.
Let me know if the save file update doesn't work and I can upload a version to my own drive.