I have recently added a set of tunables that might influence the crashes:
https://github.com/M4rtinK/modrana/issues/52

The general idea is that one can either set them to a lower value than default and the crashes might not trigger or do the opposite and try to find a reproducible crash scenario that could be used to find the root cause.

Also note that the non-default values are kinda experimental & some non-default value combinations might result in weird behavior.

So the general recomendation is to backup ~/.modrana before playing with them & to have the debug log (Options->Debug->Logging) enabled at all times to catch any interesting errors.

The slowness on Sailfish OS was caused by incorrect Python bytecode being generated (for 3.3 vs the 3.4 used on Sailfish).
The Maemo package has been using the same technique for ages to make startup faster.

On the other hand I've also spotted a few more opportunities to make general modRana startup faster on all platforms, usually by deferring stuff done during startup for later or mooving it to threads.
So you can look forward to more generally usable startup speed improvements in a future modRana update.