I can confirm the issue. I've reproduced on a clean, current 4.2-dev without any .htaccess and without url rewriting but with sef urls on, and Blog sample data installed.

I have created 33 copies of the "Millions" article and then used batch processing to assign the "Millions" tag to all of these copies, so I have 34 articles tagged with that tag.

Then I clicked in frontend on the tag in one of these articles to get the tagged items list view.

URL is index.php/component/tags/tag/millions.

The page looks fine and I get pagination for the tagged items list.

Clicking on the arrow button for going to the next pages results in a 404.

URL is index.php/component/tags/millions?Itemid=101&start=20.

So somehow the tag between the tags and the millions part of the URL's path gets lost when paging.

Adding that in the browser's URL field results in the correct page being shown.

So the URL has to be index.php/component/tags/tag/millions?Itemid=101&start=20.

somehow the tag between the tags and the millions part of the URL's path gets lost when paging.

This is what it looks like from no-IT guy. As we all have ( solid ) IT exp, we can use IT jargon......... info regarding tag is not stored/transmitted properly; in other words USMS is a fiction here.

Additional info: With SEF URLs switched off in global configuration, everything is fine, i.e. no 404 when paging.
URLs are index.php?option=com_tags&view=tag&id=2:millions on the first and then index.php?option=com_tags&view=tag&id=2:millions&Itemid=101&limitstart=20 on the 2nd page.

@richard67 many thanks :) You have just proven me right :)

@wojtekxtx Your comments are not really helpful.

@wojtekxtx Your comments are not really helpful.

@richard67 They are not helpful to you. Dont speak on behalf of others please.

#39114 should fix this. Please help testing that.

Closing as having a pull request. Please test #39114 . Thanks in advance.