Guru 5.2.5 is not compatible with joomla 4. Actually, you can upgrade to guru 6.x without any issue, because we released a new version of ja sensei that's fully working with latest guru. But in your case, there are some complicated customizations were added to the layout. You need to recheck and add them manually to new layouts, not only use old path.
I wish it was that easy, but we updated Sensei and updated iGuru.
We didn't even add back the customizations and the URL's started looking funky.
Are you saying that it might have been one of the core files that we might have previously changed?
Then when we updated iGuru it didn't change to the newer version?
Any chance you can help with this migration?
At this moment, the videos we shared is all that has been completed on the stage site.
So you are free to look into it and let us know what you think.
By the way, I owe you a couple cups of coffee for all help along the years..