Half of video turned black and is unusable

I was making a side-by-side video. After I dragged another clip into the timeline, this happened:

The whole left side of my video is black. Or rather, the whole video is now shifted half a screen to the right. I can’t do anything about it. Even If I remove all filters from a clip, I can still only see its right half.

Apart from that, the text “July 2020” which is a text filter attached to a few clips, is now shown in ALL clips, even those it’s not attached to.

I’ve seen quite a few bugs in Shotcut but nothing like this. Is this fixable?

You have a funnel (Y) icon in the top left corner of the timeline in the block with the name “Output”. Click it and see Filters. You accidentally added a filter there. Pay attention to selection in Shotcut, and use the forum search (this is a common problem).

Wow I had no idea it was possible or how the filters got attached to it, but that was it. Thanks!