Sometimes, two page-move log entries (& dummy revisions) appear to be being created for the same page move.

Examples from enwiki (https://quarry.wmcloud.org/query/93907):

• https://en.wikipedia.org/wiki/Special:Log?page=Talk%3AK%C3%A9vin_Moeson
• https://en.wikipedia.org/wiki/Special:Log?page=Ape+Escape+On+The+Move
• https://en.wikipedia.org/wiki/Special:Log?page=Draft%3APrecious_Molepo
• https://en.wikipedia.org/wiki/Special:Log?page=User%3ANinjastic_Ninja%2Fsandbox01
• https://en.wikipedia.org/wiki/Special:Log?page=User%3ACurbon7%2Fsandbox%2FHiroko_Mori

Open questions:

1. Which codebase is causing this behaviour? I.e., is it the page-moving functionality in MediaWiki core itself, or is it being caused by an extension that's installed on Wikimedia wikis?
2. What's causing this behaviour? Is there something specific that needs to happen for this to occur? and/or, is there something that - when it happens - increases the chances of this behaviour occurring?
   • Random thought; could this be being caused by a race condition happening somewhere?
3. Is there something here that's specific to page-moves, or is this a more general 'log-duplicating'-type-bug, that seems to (maybe) occur more often with page moves than with other types of log event?

(this bug report split from T395112: History merges appearing twice in non-page-specific log entry lists is confusing)