Pretty common, I just "helped" (I supervised) a mate do one the other day, and that's what was wrong, he replaced the entire kit and it pumps like a new one now.
Just to finish this post off.
This was the reason I had no water flow.
The half round little key (pic below) let go and impeller just spinning on shaft.
Image1634582305.742754.jpg
Shakey - If only I lived near the coast
Pretty common, I just "helped" (I supervised) a mate do one the other day, and that's what was wrong, he replaced the entire kit and it pumps like a new one now.
Did you have a go at it yourself Shakey..?