That doesn't sound like a bug (but there may be room for improvement all the same).
See the Changes to the Default Formats section of the Folder Formats FAQ.
Let's say you have a content format and a default format and just call them Content and Default. If you're viewing a directory which matches both Content and Default then Content will be used. (If that isn't obvious to anyone reading, have a read through the FAQ and come back to this post.)
So you're in a lister where Content and Default match, and Content has been applied. If you then change the format in some way, such as changing the view mode, then you are no longer using the Content format. You've created a temporary format on-the-fly in a lister where Default matched. (Your temporary format happens to be derived from Content but that doesn't change anything; you're using a temporary format now and Content is out of the picture.) If you now change directories to another one which matches the same Default then your temporary format will continue to be used, as per the rules under Changes to the Default Formats in the FAQ.
Could this be improved? Maybe. You could argue that Opus shouldn't do this if you start from a Content Type format but how many on-the-fly changes are needed before you are no longer considered to be editing the original Content Type format? (See: Ship of Theseus)
Maybe the whole Changes to default formats thing should be dropped altogether? I'm not sure. Personally, I'd be happy if Opus started from scratch every time I changed directories and ignored all existing context. If I wanted to make a change and keep it then I would explicitly enable the format lock. I don't know if that would be best for everyone, though. If you add a column and then change directories, and no other formats are involved, then you might expect that column to stay there which is what the current system gives you.