Hey @pvuorela , i just upgraded to 5.1 (didn’t realize it was out, these releases are coming fast!) and the issue is completely resolved! I added at least 20 tracks to my playlist and no crash at all. So i consider this resolved, and we can leave the thread alone now 
(but at least anyone else who stumbles onto this issues sees the start and end in all one thread without having to jump around and will know to upgrade).
Thank you and anyone else who fixed this, and being willing to help me troubleshoot further. the audio player is my primary usage of Sailfish, so this is a huge quality of life improvement. Again, if gapless playback ever comes, perfection! Lol