Forced by whom?
Version 1.21.0.3744 is not new. It can be considered “ancient” by now [1.21.0.3744](Plex Media Server - #382 by emilybersin
I myselfd have no experience with Synology NASs, but you might want to take a look at this Synology FAQ - Questions, Answers, and a few How-To's
