Audio keeps being set to 78% (specifically 78.0221%)

I have no idea why this is happening, but everytime I open this specific file, it slows down to 78.0221%.

Most likely it is the (fairly new) “automatic tempo detection” that is causing the problem. See this post on GitHub for a workaround: Unable to import song at correct tempo if wrong tempo detected · Issue #6425 · audacity/audacity · GitHub

I don’t get a dialogue box to press Yes on, and when pressing Ctrl+Z it just deletes the audio.

Sorry, I didn’t mean that part.

Then try importing and hopefully it will be imported without stretching.