It's a long-standing bug that also affects me. It's quite annoying since it's easy to irreversibly hose up your sync account by going over the remote storage qu

It's a long-standing bug that also affects me. It's quite annoying since it's easy to irreversibly hose up your sync account by going over the remote storage quota. Maybe you don't have a Firefox account and/or sync setup? There are related issues opened for Temporary Containers, MAC and Firefox and at least from the public discussions not much is happening about it.