I experience this problem for years.
@MBH: Thanks for reporting this. Please use the bug report form (linked from the top of the task creation page) to create a bug report, and fill in the sections in the template, instead of deleting them. Thanks. Cannot reproduce in Firefox 126. What's in the error console of the browser developer tools, which browsers have you tested and which versions, does this also happen in safemode?
Now it happen on https://ru.wikipedia.org/wiki/%D0%9D%D0%BE%D0%B2%D0%BE-%D0%90%D0%B4%D0%BC%D0%B8%D1%80%D0%B0%D0%BB%D1%82%D0%B5%D0%B9%D1%81%D0%BA%D0%B8%D0%B9_%D0%BA%D0%B0%D0%BD%D0%B0%D0%BB . Console:
Ново-Адмиралтейский_канал:584 This page is using the deprecated ResourceLoader module "codex-search-styles".
[1.43] Use a CodexModule with codexComponents to set your specific components used: https://www.mediawiki.org/wiki/Codex#Using_a_limited_subset_of_components
(анонимная) @ Ново-Адмиралтейский_канал:584
startup.js:1307 This page is using the deprecated ResourceLoader module "jquery.ui".
Please use Codex instead.
execute @ startup.js:1307
VM940:4 Uncaught TypeError: Cannot read properties of undefined (reading 'innerHTML')
at <anonymous>:4:45
at globalEval (startup.js:1134:17)
at runScript (startup.js:1285:6)
at enqueue (startup.js:1172:5)
at execute (startup.js:1392:5)
at doPropagation (startup.js:748:6)
startup.js:1307 This page is using the deprecated ResourceLoader module "mediawiki.ui.button".
[1.41] Please use Codex. See migration guidelines: https://www.mediawiki.org/wiki/Codex/Migrating_from_MediaWiki_UI
execute @ startup.js:1307
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app.js:291 One instance of Convenient Discussions is already running.In safe mode map doesn't work at all: https://ru.wikipedia.org/wiki/%D0%9D%D0%BE%D0%B2%D0%BE-%D0%90%D0%B4%D0%BC%D0%B8%D1%80%D0%B0%D0%BB%D1%82%D0%B5%D0%B9%D1%81%D0%BA%D0%B8%D0%B9_%D0%BA%D0%B0%D0%BD%D0%B0%D0%BB?safemode=1#/maplink/0