Why is this title dissolve transition still visible in the clip after deletion?

Hi I'm new to FCP so please bear with me.
I have a simple clip - just a video sequence with some titles overlaid.
If I attempt to delete or otherwise change the title,  the state prior to deletion is still visible in playback.
Here's a video demonstrating what I'm talking about.
There are no additional elements outside of the crop shown. It's literally just the video along the bottom and the titles connected to it.
I looks like a bug to me but I'd be happy to be corrected, otherwise I'll have to bail out and go with an alternative to FCP.
Many thanks.
www.youtube.com/shorts/zr1kbagdHgw

Looks like you've got some render files hanging around, which can be deleted. Also, if you've got reasonably recent hardware, go into prefs and turn off automatic rendering. For most formats, it's entirely unnecessary.

Had something similar to that a few years back that stumped me as I don't ever do background rendering that could account for the ghost dissolve. Persisted after deleting any render files.

Compound clipped the sucker. Quit FCP. Opened FCP. Broke apart the CC. Quit then open again and ghost-be-gone. Beats me what caused it but it's never haunted me since.

If that doesn't do it export an XML, quit, then import that into a new project. (It's a bit dramatic abandoning FCP because of a glitch. This forum wouldn't exist if folk gave up that easily as they'd have moved on to another NLE which, as someone who also uses Resolve & Premier, has their share of anomalies as well.)