Affects 1.21.61
The one pack I previously attached had the same bone path which worked just like you said.
This bug still occurs. I might have added the wrong pack so I replaced it with a problematic one. It seems that the baby held item also breaks if the bone path does not match the bone path of the default model.
Affects version 1.21.44.
Mentioned in MCPE-46218 as well but it was closed.
I also just noticed this bug in ibxtoycat's video lol
Why is this still not fixed?? It's fairly simple to fix.
P.S. Affects 1.16.3
Affects 1.21.71