I tried to use tags with uppercase such as ‘BMW’ and it seems really buggy, with the tag not even being found at times. Also the order of the tags is weird. Some of them are alphabetical, others aren’t. I created them in alphabetical order so it shouldn’t be down to their ids.
Update
My installation had got into a very weird state with Tags. I went into Rails console and destroyed all Tags from there and behaviour seems to be back to normal. Will report back if it changes again.