Firefox 71.0 64bit, no addons, on Win10, 1909/18363.476,
pveversion: 6.1-3/37248ce6/5.3.10-1-pve
"Funny":
- on private session, no success
- cleaning up cache, no success
- cleaning up cache, waiting 5 min, success
Firefox issue ... I suppose. Maybe it is time to remove it from my desktop. Thanks to tom!