Hello Florian,
Matija,

> > > all of a sudden it stops and raises an exception - could you also
> > > try that and let me know, thanks    

> > Yes, after 5 minutes animated-paintable.scm crashes.  Hmm.  

> Ok, thanks for trying - This is going to be quite a lot more complex
> to debug and fix, and i may need the help of some guile/goops guru ...

Actually, not as complex as i initially thought ... and I believe I fixed
that bug too, commit 655aaf64278562fdf15d64d976ccb71c3dcee7eb

If you could kindly grab the latest, run the make/install dance on your
respective distro and try again ... Here the example now runs for hours,
as it should, consuming +/- 3% cpu and a steady 0.8% of mem (so afaict,
no memory leak either).

Thanks,
David