I temporarily pasted a PCB from another project. Since the two need to fit together, I just wanted to quickly check how things lined up.
I deleted the PCB, but now there are a ton of errors where it used to be.
I tried deleting markers and running it again. I tried closing Kicad and re-opening.
What are some other potential solutions I should try?
From your screenshot, there is a [Delete All Markers] button at the bottom of the DRC checker.
Euhm…
So you already did that, and also:
(Almost) all your DRC violations are about “Track has unconnected end”. So my next guess is that you did not delete everything, but a lot of track segments are still present at a hidden layer. Do you have copper layers that are set to invisible in the Appearance Manager on the right side of the PCB Editor window?
I think you’re right about me not deleting everything. Since I pasted a 4 layer board into a 2 layer board, they may be from layers that don’t exist in the appearance manager. Maybe that’s why I can’t see or do anything with them.
Update: I copied the PCB, deleted everything using the global deletions tool, then pasted it back in. That seems to have worked.
It’s possible to enable the inner layers in Board Setup → Board Editor Layers afterwards. The items which are in the original design (file) become visible. You can select and delete them, and then disable the layers from the setup again.