Ok so I MAY have finally found a solution, (I want to stress MAY as I've now tested for about 10 minutes and so far it's worked). So go into settings > Apps then select "sort by" (the little thing like 3 lines with a funnel icon) and turn on "show system apps" search for Android System Intelligence - go into it and enable all its permissions (it's probably only related to one or two but I enabled them all), then close all open apps and give it a go. For me the first time it showed "no suggested contacts" for about a millisecond before it showed them, and so far, repeatedly closing out the gallery fully and reopening it's still working!
EDIT - I just had 1 hiccup where it wouldn't show them again for sharing from a notification, so may not be a true fix but seems to make it work more often than not!?
EDIT 2 - still getting the odd hiccup with nothing showing up, but cleared the system intelligence cache aswell and performed a restart, definitely seems to work more often than not now just still not 100% for some reason.