I have a pixel 6a, and also experienced strange behaviour saturday june 14th. I live in Norway and enroute Trondheim, the gps was way off, atleast 50-200 meters. (varied) using OSM. It was actually useless for street navigation.... No SUPL, but the graphene PSDS activated. This has worked fine for a very long time. On the 15th I activated the proxy SUPL in hope of getting the OSM to work navigating the city. It did work, but reading this thread, I think the explanation is something else that just switching on SUPL via proxy. Now I can turn off the supl and have only PSDS and it works. I do use VPN, and on the 14th the exit node was a country in Asia. Not sure if OSM or Graphene use IP to choose correction. Usually I just have a local exit node, just wanted to mention it.