FTB sent me a Notice of Proposed Assessment related to my 2017(!) return. Apparently I had taken a deduction that the FTB decided was invalid. After researching and concluding the deduction was indeed invalid, I went on their website and paid the balance including the interest.
Then a month later I got a Balance Due Notice informing me they would soon pursue collections actions against me, e.g. garnishing wages etc. Looked online, showed I still had a balance. Check bank account, sure enough, they had deducted it. Payment history on their website showed the payment, but status was "Suspense".
Called them several times, each time was told they were too busy to take my call, try the website. On my second attempt I finally got someone on their chat system to release the funds. Apparently, their practice is to release the funds only when you file your next tax return... but in our case we moved out of state, so they potentially would have started forcibly collecting money that I had already paid them.
Cool agency.