Troy-Bilt Pressure Washer built by Briggs & Stratton Unique Spray Problem?

Troy-Bilt  model: 020414 Built by B&S   Gas Powered.
When Wand trigger is first pressed, Spray is normal. When released and then pressed again, the trigger is hard to press. Then after several seconds a tiny water stream comes out then a few seconds later it blasts a normal spray.This will repeat itself as described everytime. If you wait 30-40 secs it will spray normal again when 1st pressed, until released and pressed again and problem repeats. No clogs, hoses and supply water ok. Have removed Unloader valve, disassembled and checked. Looks ok. Spray pressure ok when it is spraying. Operation seems fine otherwise. Am I the only one having this problem? (replacement unloader valve is not available)