Thank you all, Appreciate the feedback and help.
I have been using the bike this past weekend through parts of cederberg and tankwa.
This morning I gave the bike a proper scrub. At the same time, I dialed the compression and rebound on the front and rear suspension all the way in, and then set it up again from there.
Took the bike round the block to get it dry and some heat into the drive chain before I lube it again, and it feels as if the notch feeling is gone. What the fudge... Baffled.
Will take it on a proper run over the weekend to confirm.
Perhaps just better to replace the bearings anyway with a bike being 8 years old and 36k on it ja?