I finally opened this one up and took a look inside.
The PSU voltages looked fine on the oscilloscope and I couldn't see anything obviously wrong there.
I still experienced some resets/crashes but they seem completely random.
I have always been interested in electronics and synthesizers. I studied electrical engineering in the first year of college but I dropped out due to poor motivation, not liking mathematics and laziness and things like that :)
A while later I started studying Computer Science which I eventually got my degree in.
Recently my interest in music and electronics started to come back and I am sort of trying to pick up where I left around 15 years ago.