Some taxonomy term pages don't show all associated nodes

There are so many reasons this could happen I'd need more information.

Assuming you are using the default taxonomy view page look at /admin/structure/views/view/taxonomy_term first to check and test.

If you left the default Content Teaser display style in the view, you may want to take a look at the content type display at /admin/structure/types/manage/[content_type_machine_name]/display and see if the Teaser type if enabled is displaying anything.

Its also possible you modified some twig files.

Also verify that the converted nodes are still tagging the term and if not its possible that the term data was not mapped properly in the second step of the convert bundles form. The default is to remove the data if the field name is not the same. When it isnt the same field name you have to select a field to map the data to if one of that type exists.

If the last item is the case, hopefully you have backups or revisions.

Hope that helps

I use the default taxonomy term view with no customization whatsoever. It's display setting is indeed a node teaser.

I use the default node display settings for all content types and further more --- one node of a certain content type is shown in the taxonomy term page but at least one other node from the same content type aren't.
I have repeated this finding with two other content types.

The only Twig file I have modified is themes\globalrs\templates\layout\page.html.twig and the changes there are minor such as adding an HTML-CSS structure and perhaps printing a Drupal region in it. Nothing more.

I no longer recall which nodes have been converted exactly and can't access any relevant logs as I have already removed the module several months ago just after converting the nodes but based on searches with the Drupal search engine I get the impression that no tag was deleted anywhere at all.