We have just moved from v17 to v2021.1 and have experienced this. In our case it appears to be related to the Sync Windows tool, as having it loaded causes the legend to appear, even when not actually syncing. This tool also has embedded legend controls similar to those in the Legend Manager Tool, which look to have appeared in there in v2019, and removing the legend from here or the right-click option causes the legend to reappear following a map pan / zoom.
The knock-on effect are the warnings / errors thrown when adding this map to a Layout, being the Reparenting to a frame, and then the Unable to clone Window.


Searching support I can only see a post stating embedded legends aren't allowed in 64-bit Pro so a decision must have been made to allow them and add the controls to the Sync Tool in v2019:
https://customer.precisely.com/s/article/Resolve-issue-where-an-Embedded-Thematic-Legend-feature-is-missing-in-MapInfo-Pro-12-5-4-64-bit?language=en_USFor now I'm using the version 17 Sync tool with v2021.1 with no legend issues, however it would be preferable to have the latest version working correctly as it's become invaluable to our users working with multiple map tabs.
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Darren White
Derbyshire County Council
MATLOCK
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Original Message:
Sent: 08-25-2021 09:48
From: Rex Edwards
Subject: Show Legend
Yes - it works temporarily - if I Tab the window it reappears. Will work for now.
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Rex Edwards
CAMPBELL AVIATION GROUP
Alexandria VA
Original Message:
Sent: 02-17-2021 13:23
From: Rex Edwards
Subject: Show Legend
Is there any way to change the default that always shows the legend in a map window (which can be disabled by clicking "Show Legend for This Label")? Also how can I disable the "No Active Legend" that appears in the Map Window (and any saved windows)?
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Rex Edwards
CAMPBELL AVIATION GROUP
Alexandria VA
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