When running a multilanguage site, the URLs for tags are not always correct
From Joomla! Documentation
When linking tags, URLs are different now than they were in 4.2 on a multilingual site. Especially, when using the Popular Tags module, links are different now.
This pertains only to Joomla! version(s): 4.3.0, 4.3.1
What is the cause
The router has been rewritten to fix major issues in the way URLs were created for tags, especially when several tags were associated to a single menu item.
How to fix
The fix is coming in 4.3.2.