See
I am getting errors with my calibre library on a networked drive/NAS? in the calibre FAQs. And, yes, you can find quite a few people posting after the dancing bear stops dancing. calibre is intended to be a single user application with local storage used for the database/library. The calibre content server is the recommended method of accessing your calibre library from other computers.
Since you are mentioning accessing your library from wherever you go, where is your Docker container located if not on your LAN? If it is external to your network, it is even more likely that you will run into issues.