I have stumbled onto two issues.
The first issue is when I try to load the LV2 plugin in Carla, the plugin works as it produces sound when I feed it MIDI. But when I want to open the UI it simply won’t open it and locks up Carla when you try to close it.
The second issue is with the VST3 plugin, this one works and the UI opens as well. The only problem with this one is that it does something weird with scaling. I like to have it set at 200% scale, but I can only get it to stick on 135%.