You have been lucky for several years. As Jay mentioned your Docker is outdated and requires a hard update vs a GUI soft update.
The creators of Discourse even state explicitly that you need to once and awhile so command line updates. I have in my over 7 years of use in the early days have observed the web GUI specifically tell me that I need to do a command line update. And you also need to at times perform an OS upgrade(or create a new server to refresh OS and move Discourse to it)
This is one of the cons of Self Hosted is you as the Self Hosted have to maintain the backend and fix things when needed or goto Marketplace and pay someone who has the skills needed