On what web browser?
Does the error happen immediately, or do you have to go through some number of slides and/or steps to reproduce it?
Does it happen on any gallery slideshow, or just a specific one?
Are videos involved? If so, what kind of videos? (YouTube, mp4 uploads, ...?)

Currently Firefox. Takes a few seconds after clicking the buttons for the error to appear. New install with 4 Youtube videos. Nothing else to compare against though not had this happen before so assumed it might be a bug.

Just tried again and the error link shows a merge of titles:-

22: InternalError: too much recursion
index.php?page=galleries&type=video&id=miasthenia%2Faesmah-nameless-echoes&slideshow=1&wide_high=1

Miasthenia are a different band to Aesmah, shouldn't be there. Could it be titles like "Luxúria" and "Katún" causing the issue?

I couldn't reproduce a too much recursion error, but I did find issues with YouTube videos in the slideshow which I've fixed in #5002.
Possibly it will correct your issue, as the bugs may have led to a different outcome for you for some reason.
If it's still occurring please let me know a URL I can directly test.

As for URL monikers being wrong, "miasthenia%2Faesmah-nameless-echoes" implies "aesmah-nameless-echoes" exists in a category "miasthenia". It's hard for me to comment without getting deep into that.

Sorry, this was my hosting and their Web Optimisation altering the URL's. 2nd issue was a Moniker I thought I'd changed. No obvious issues elsewhere but disabled the Web Optimisation so slideshows now work without issue. Thanks for the fix ;)

"themes/default/templates_cached/EN/ajax_ssl.js,q1666879827.pagespeed.jm.Mh3z4jbeDl.js:1"

Ok, well the slideshow code has been completely rewritten for v11 anyway.