Placing structures that were serialized before 1.19 by structure blocks will log the following in case the structure tries to paste item frames.

[20:17:53] [Server thread/ERROR]: Hanging entity at invalid position: gt{x=-75, y=15, z=-55}
[20:17:53] [Server thread/ERROR]: Hanging entity at invalid position: gt{x=-75, y=15, z=-56} 

As far as I've tested it doesn't affect said item frames since they seem to work as they priorly did. It seems to just be a console log.

Code analysis

Code analysis by TelepathicGrunt can be found in this comment.