Right now you have to edit a topic twice until a "edit" appears under the history.

So you edit a fresh topic, check the history > empty:
Then you edited the topic again, check history > topic was edited 5minutes ago.
But it doesn't show the current edit. And so on. A bit strange.

We tested it in our local copy, it is working correctly.

Can you check if the edits are recorded in the database ?
Check for any new entries after first edit in the table codo_edits

Yes the edits are recorded. When you start and edit a new topic the history works correct. But the 3.4 topics are bugged.

Are they recorded even for the first edit of an v3.4 topic ?

Can you check if there is any difference in the data on second edit in codo_edits ?

The history is empty if you check the history of an edited 3.4 topic. After editing the topic again the history show all old edits but not the current one. Inside the database I see no difference.