@Christoph-Hart Weirder and weirder!
Now I got an interesting one, without the snippet browser (just stock Hise):
I opened Hise with SECONDARY project
Then loaded MAIN project, open XML, and start working on Graph/SNEX
Got a hard crash after compiling in SNEX (if it can be important)
Re-open Hise with MAIN project, open the Graph
BOOM!!! It's been replaced by SECONDARY Graph!
It's like the SECONDARY was still in memory before the crash.
I am only talking about opening project's XML here, I never use .hip, so it cannot be an "automatically saved preset thingy"...