Quick update: I just manually ran another system-wide backup and it was successful, so it seems it may have just been a one-off and probably won't happen again anytime soon, was likely just coincidental I was making a bunch of changes to it yesterday considering other system backups proceeded without issue since the time I made those changes. But I'd love to get a second-set of eyes for insight into if this is something I should fix to prevent it in the future or just a one-off type of thing that can safely be ignored.
@nebulon Will do. 🙂 I've checked today and see the sync tokens grew a fair bit again, although right now performance seems to still be okay. So I'll monitor a bit over the next week before filing a ticket just in case it grows back to where it was but still syncs quickly, as that may indicate something related but different as a root cause.