The arrow doesn't lose its momentum until it hits a character or disappears. If the shield gets dropped the arrow just continues. It's not a glitch or a bug. It's been like that since the game came out
Tbh playing her my biggest issue is with junkrats and pharahs.
Long range splash damage that I can't do anything about and the shield can't block well. Rein is an easy target if you know how to get around him and smashing bastions is my new favorite thing.
I’ve seen her shield make Moira’s damage orb disappear. I can’t ever beat her 1v1 with Moira. I rarely beat her with Reaper, who is normally a tank killer. She’s a pain in the ass to beat when someone is decent with her.