I have multiple PCs running, all have firefox sync running and are on auto update. Since version 100 I have firefox profile issues on all PCs. If firefox is open it stops responding without any notice. After closing and re-opening i get message that the profile is not compatible and firefox cannot continue. I then need to quit, and download the latest Firefox version manually using MS Edge ! Only then I can restart firefox and this reads my profile fine. So the profile is not corrupt or missing ! I guess it is caused after one of my PCs is auto updating first and then saves profile in new version format which is not compatible with the previous version still running on my other PCs. Why was this never an issue before version 100 ? I hate to disable auto update nor do I want to loose sync. Cannot find this issue on your support pages or the web. A fix would be highly appreciated ! Greetings, Arne van Belle