I'm pretty sure it is the impeller. I think it is a little unbalanced.
I removed it and the ceramic shaft. I held the shaft between thumb and forefinger (held the ends), with the impeller on it and then spun the impeller. I could feel an unevenness and variation in the spin
The impeller does not move on it's shaft thingo like my 1048's, so I don't think the mod will do anything.
I think a replacement impeller is probably needed.
I suppose it comes down to whether the pump could be damaged, or it's pumping affected by this? I doubt it, and the noise is not audible above other noise unless close to the pump.