I suspect that URL is using a multibyte buffer somewhere, and that leads
to ... problems.


In GNU Emacs 28.0.50 (build 52, x86_64-pc-linux-gnu, GTK+ Version 3.24.20, cairo version 1.16.0)
 of 2020-08-19 built on xo
Repository revision: 9c17df59a38b71166c8e4644ab525e791f7ff21c
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Debian GNU/Linux bullseye/sid

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no