Re-checked in betalabs cawiki (and also just general testing for patrolling) - could not reproduce.

The tested scenario - I tried to stick as close as possible to the ticket description:

• in betalabs cawiki find a page that was converted from LQT to Flow (e.g. Talk:ET8)
• from a Board description delete the template {{Pàgina de discussió en wikitext convertida a Flow|archive=Ajuda Discussió:ET17/Archive 1|date=2015-06-21}}
• as a user with patrolling rights, go to 'View history' and click on 'prev' for that change
• a compare-header-revisions&header_newRevision page will be displayed; 'Mark as patrolled' links will be displayed
• click on 'Mark as patrolled' link - the change will be marked as patrolled.

Thanks for merging in the duplicates, could not find the correct task but suspected there must be one. :)

Change 301868 had a related patch set uploaded (by Sbisson):
[WIP] Fix patrolling links

https://gerrit.wikimedia.org/r/301868

Change 301868 merged by jenkins-bot:
Fix patrolling links

https://gerrit.wikimedia.org/r/301868

Checked in betalabs 1.28.0-alpha (2c35abe) - patrolling is enabled only cawiki( via Recent changes).

Checked

• T133606: Patrolling of topics from Flow gives "Session failure" and T134921: Patrolling of Flow-contributions fail.
• general patrolling functionality
• 'Recent changes' links to diffs with 'Mark as patrolled' links

Note: The confirmation sliding popup displays a cryptic topic title, not the actual topic title. Per @Catrope, the issue is outside of the scope of the ticket.