Sorry to hear of your clunky wheel problem. I’m pleased to know that your wheel has had so much use it has developed this problem. What has happened is that the 1/8″ diameter silver steel hub pin has worn the hole in the mild steel crank such that it is oversize and allows the pin to clunk.
A simple but temporary solution is to remove the hub pin and hit it with a hammer so that it has a slight banana shape. Then tap it back into the hole.
A better and permanent solution is to order a “Clunky Wheel Kit” from your local Ashford dealer. This kit includes a new crank, hub pin and con rod. It’s easy to fit and will make for silent spinning.
The best option (apart from buying a new Ashford wheel) is to fit a “Double Treadle Kit” which includes the parts mentioned above plus double treadles to make for effortless and quiet spinninge