Looks like it is UE-289895
https://issues.unrealengine.com/issue/UE-289895
(Bug created on May 23, 2025)
Seems like the Licensee was also kind enough to post a (potential) fix for the bug.
Shame no one included it in 5.6
I mean, completely breaking an existing feature, that’s something you would expect regression testing to have caught, no?