I'm really surprised so many people are reporting problems, since I've had none at all!
I originally started with version 0.11.1Public-pc, then upgraded to 0.12.3-pc, and then
0.13.0Beta-pc.
My PC is old and weak (2 core Intel Pentium G2030 cpu, 8GB ram, 2TB disk, motherboard graphics).
I'm running the Linux version (on Ubuntu 20.04).
Here's what I do (in case it helps anyone out there).
When a new version comes out, the first thing I do is make a backup of my save data.
For example: TheHeadmaster-0.12.3-pc/game/saves/
Then I unzip the new version into a new directory, never on top of the previous release.
For example, TheHeadmaster-0.13.0Beta-pc
There will initially be no save directory. I copy my backup from the previous version into the new version,
for example: TheHeadmaster-0.13.0Beta-pc/game/saves/
Note that renpy on linux also saves data to ~/.renpy/, so you might want to back that up also.
I've always played the game as far as possible at each version, so when an update comes out, I can load
my old save and continue from where I left off.
I launch the game from the command line by running the TheHeadmaster.sh script.
I've also played the Halloween and Christmas add-on games.
I've never had a crash, never had a lock-up, and never had any lag.
If I ever got stuck in the game, the walkthrough/guide was all I ever needed to continue
(usually you just have to advance another part of the story in parallel)
RenPy is python-based, so should be portable across operating systems. It's also self-contained, so you shouldn't
have to install or configure anything.
Is it possible that some folks are unzipping new updates on top of older versions, and corrupting some of the data files?
If so, maybe try keeping each update in it's own folder, and just copy/paste the saves over.
Good luck!