We have another issue related to docker not upgrading because of unmet deps.
Check journalctl -fa and if it shows something like below over and over again:The following packages have unmet dependencies: docker-ce : Depends: libseccomp2 (>= 2.3.0) but 2.2.3-3ubuntu3 is to be installed E: Unable to correct problems, you have held broken packages.
To fix:apt update
You might have to run the above command a couple of times since it might says it cannot get the lock. Once the update is done, it should update automatically.