Hey I’d be interested to know if this the issue with your shifter cos I’ve never had this part fall off any other shifter that I own or have owned, wondering if this is a fault with GRX shifters
So, 5 months on, warranty claim was successful. Retailer received credit from Shimano and has passed it on to me. It's at trade amount, so doesn't compensate for what I had to pay to get a new shifter, but it's something. They didn't say what the fault was.
Cheers, could be that. Day before had the bike upside down doing some cleaning so may have fallen out then