After this latest patch (I believe), VRC Parent Constraints do not work. Like as if I don't even have any on my avatar. Same problem also exists in SDK 3.7.3 and 3.7.4, but work fine in 3.7.2. Was able to find a workaround in 3.7.4, where it acts correctly in Unity. However, in-game has same results of them being non-functional, regardless of if they work in Unity or which SDK they're uploaded with.
First three pics are 3.7.2 and pre-1552. Latter three are 3.7.4 and post-1552