It depends on what kind of bugs you've introduced but the "UI way" would be to go to Ctrlpanel > Basics > Info and look at very bottom there to investigate which shadow tiddlers have been overwritten, i.e click the little magnifying glass.
Then you can delete one of those tiddlers at a time, and save+reload, to see if it helped. What happens when you delete a manipulated shadow tiddler is that it resets it to the original.
Before everything, you should of course update the wiki to latest version.
You mention backups so I assume this is already taken care of, which would be the very first step.
If your bugs are of a more serious kind where you e.g have manipulated the file content via an external editor then I'm not sure what to do.
<:-)