I've moved to a new PC and moved my MusicBee library over, all fine apart from the group-by year functionality now puts all years in 0-9 instead of separating them by year:

How it worked on the old computer:

I've tried going round the houses a bit with changing the grouping/sorting and changing it back to no avail. From what I can see, all the settings are identical between both versions. I've also speculatively rescanned the entire library.
Was previously on 3.5.8447, am now on 3.6.902.
Struggling to figure this one out, can anybody help me?