The mostly likely cause (and unfortunately the hardest to debug) will be "some radio issue in your environment" .. it could be interference or loading on the AP or proximity to other devices or too-strong a signal or .. ![]()
To investigate you'd likely need to run iwd in debug mode, which will generate mountains of debug log output, which probably nobody on staff will really understand (as none of us are wireless engineers).
Pi is close-enough to run a short cable? Ethernet really is the best solution to WiFi problems (though never the answer people want).