That slowness is because Epicor is calling for one row at a time. You can put a BPM in there to fix it. I can never find the post, but I have the BPM in place. Below are the screenshots. That takes it from minutes to literally seconds.
edit: here is is. References Dialog Speedup - Works -> (Need a ̶C̶l̶o̶u̶d̶ Guinea Pig) :dumpster_fire: - #33 by klincecum