You don't need to use a bullseye for NPCs to target your nextbot. Add the flag FL_OBJECT to your nextbot then you will be able to use npc:AddEntityRelationship(self, D_HT, 99) without the bullseye.

Also you should use NextBot:BodyMoveXY, that way SCP-049 legs will match its movement when walking. (the swimming animation looks kind of bad tbh)