Wilfa Uniform - Sounds like it's struggling after recent clean.

Looking for some troubleshooting advice. I've had to spend a lot of time away from home lately so haven't been taking as good care of my Wilfa Uniform grinder as much as I usually do, so I gave it a rather thorough clean at the weekend after months of just letting it build up.

On Monday I noticed that when grinding it sounds like it's struggling; as if there's a bean in there that's catching and throwing things off every second or so, even when there are no beans in there. It's not a motor whine or anything like that; the only way I can describe it is it sounds like it's grinding on empty, and then suddenly coming into contact with something every now and then. I've opened it up and cleaned it out again and there's no signs of a anything obstructing the burrs, and no sign of damage. It still seems to be grinding fine, but the sound is pretty worrying.

I think I might have accidentally cleaned off some of the lubricant on the ball bearings, but this is purely just a guess. Does anyone have any other suggestions?

Thanks in advance!