Its because of
OwningPawn->MoveIgnoreActorAdd(root->GetOwner());
On grip currently by default the gripped object is auto ignored for movement. is to prevent the character from colliding with objects he is holding and moving around since they aren’t attached to him (ie: the fling yourself into the air syndrome).
It also turns off collision with just the held component but obviously if others are attached to it in the actor they could still collide with the character without that line.
I can add a toggle for it to the advanced physics settings? 99% of the time its best as is. You found one of the few times it isn’t.
Edit I am loathe to reverse default behavior because of how many setups it could break and I really do think that turning capsule collision off to the actor on grip is what people would want most of the time.
So I just added a boolean for it to the AdvancedPhysicsSettings and enabled it by default to the doors and drawers in the level.