I tried updating LMMS hoping that it would crash less in a future update, so I tried doing a standard
sudo pacman -Sy lmms, which worked. But lmms wouldn't start anymore. I forgot what the error was at this part, but it something about Qt, so I tried reinstalling Qt5, removing & installing and now I'm getting this error:
qt5ct: using qt5ct plugin Cannot mix incompatible Qt library (version 0x50d02) with this library (version 0x50e01) Aborted (core dumped)
Not sure what else to put here as I don't know how Qt works in detail.