Hello again.
I've looked at your new overflow protection logic. It seems like you prevent the inserter from moving if it cannot insert into the target inventory. The problem with this is that the basic inserter already does this logic by default, which is why throwers had overflow protection into machines.
The only solution to this problem is actually to insert the items when the thrower releases its payload instead of when the item projectile actually lands on the ground. Otherwise, you have no idea what will happen to the target inventory while the item is in the air.
It's a bit of a sneaky workaround, but it's not really noticeable for the player.
I've already implemented this system in my fork.