Does anyone by any chance know what the screw size is as the title says? There was a thread a few years back talking about the similar issue. The forum won't let me post in that thread any more. In my case the threads seem to have stripped.

It's this
https://www.espressocare.com/products/i ... reen-screw
But it doesn't list the size.
Thanks

For posterity sake, I found out it's M4, 6mm screw. And luckily it was the problem. I had low hopes, I thought the piece it goes into may have been the issue. Mushroom something, as I think that piece is brass so I figured that would wear before stainless steel screw. But the shower screen is firmly in place now with the new screw. $1.25 saved me a $500 replacement.

This Starbucks thing keeps going strong, after at least 10 years and probably longer. Makes a really good shot too. I already decided to replace it with the Gaggia Classic Pro. But I was thinking once the Barista Athena goes caput but it just doesn't want to. And I can't see Gaggia giving me a much better shot than what I get now to warrant just replacing it while it's still working.
Blessing in disguise was when original porta filter broke and I got the open bottom one from the Seattle Coffee. I lived in Chicago then and knew baristas in Intelligentsia on Broadway so one of them came over and explained and taught me how to get a good espresso. Ever since I've been super happy with the Barista.