Hi Scott
I had exactly the same problem on mine mate. Had it back at prochem in Greenock about 4 times. Told me they had never had a problem like it before. Pump was replaced twice then within 2 days started getting the same problems.
I ended up buying a female quick connect, attaching it to the end of the solution hose then letting it run for 5 mins (making sure the solution tank had plenty of water in it).
Touch wood, this has been ok since, but I have started doing this every time I fill up to ensure it doesnt happen again.
John