Black screen after login; Can only boot in Safe Mode

Howdy intrepid support community!

My MacBook will only boot in Safe Mode and Guest mode now. When I log in normally, after the progress bar loads I'm presented with a black screen with two bands of thin, vertical lines that flicker. In Safe Mode, it works more or less fine, just a bit laggy.

I have run Disk Utility First Aid, Apple Diagnostics, and reinstalled MacOS. I deleted the only third-party app that was updated recently and emptied Trash. I don't know what else to do. Please help!

WILD CARD: a few days before this started, my laptop fell and hit the ground hard. It worked perfectly fine after that, but the next time I rebooted, this all started.

My computer: Mid-2015 rMBP running Mojave 10.14.6