Carpet bots take extremely weird knockback while blocking with a shield. If hit twice within the time of a damage tick, it lurches forward wildly. The intended behavior is that they shouldn't be taking knockback from blocked damage at all, much less moving forwards

Video example

Shield blocking sounds are also not playing

Caused by client & server desync in velocity, or rather the lack of it. In vanilla when blocking with the shield it will change the server velocity, but not update the client velocity. Here the client & server velocity is shared.