r134a I have 6-14 PWAs at various times on both default launcher and lawnchair via Vanadium. Never happened.
Some more questions for people who see this issue can be: Maybe it happens with non-Vanadium browsers? Or perhaps lower or higher number of PWAs? Maybe with some specific launcher? Could also be the websites themselves, I use actual PWAs but some websites register as shortcuts, so maybe shortcuts get wiped?