Remote access from external not working after setting Router DNS to Pi Hole

I have recently setup Pi Hole and my Router to use RBP IP as first DNS.
It seems that since then my Remote Access (over Onion Url) from external network (e.g. Mobile Hotspot) is not working. Internally I can access though.

Did anyone else have this experience? Do I need to adjust something to make it work again?

Edit: It works after several connection attempts. It is still strange though. Would be happy about any info…