Update: It’s working!
So I ran the original clip from the new video through AVCFree (some converting software) – just made it 60fps, kept the rest the same. I redid the project with the converted file from AVC and after exporting there were no issues. Amazing! I was starting to lose hope haha.
I’m not sure what the issue was/is, but on my end, bypassing the Shotcut converter solved the audio distortion.