Your comments

Under GA it works fine for me, but when trying it from GTM it doesn't work. I've turned off the setting that remembers the last container and now it works fine, so it's not a big deal.

Not sure if the new release is already out, but tThis is still an issue for me on the Brave browser. GTM reverts to the default account. No problem with GA. Version 2019.7.26

Was about to put this in. This would really be a great feature!