Now cured in Server Version#: 1.25.4.5426
Thanks to @sa2000 in Synology thread - [Plex Crashes Every 3 Days at 3:30am Due to System "Out of Memory" Since PMS 1.24.4.5081 - #124 by ElusiveZatchmo]
Didn’t fancy waiting 10 weeks + so manually ran Database Optimisation until 7GB reduced to 570MB - no issues so far.
