Hi folks, AFAIK this issue - “After saving and reloading my session, all of my ZynAddSubFX patches are replaced with default sine-wave patch” - is not 100% resolved. I first encountered it a couple of years ago and still experience it under the otherwise awesome Ardour 6.9/Ubuntu 22.04/latest Zyn with or without the excellent new fusion GUI - and the workaround at the link above (saving patches with a different path/avoiding special characters in the path) didn’t help me.
What works, I have no idea why, is to disable (just switch off, not remove) every problematic instance of Zyn before you save the project and then switch them back on after reload. And then, at least for me, the patches are there
I don’t know if anybody still encounters or cares about this issue, but I leave this here just in case it’s useful.