Unfortunately, the error bug occurs when Reverse Engineering Dread Guard Relics, period. My question above is regarding instances you get the error but also get the message that you've successfully learned a Schematic. We want to be sure that when you're told you learn a new Schematic, that you actually do! I've edited my message above to better relay that. Sorry for being unclear!
I've had this RE error issue with Dread Guard relics and have not learned the schematics. I assume it would be the same. I have seen some people encounter the issue and still learn the DG schem though.