There are two possible issues that I am aware of.
- If you transferred the pdf files to the reader using Finder (on MacOS) or the Windows File Explorer, your problem is simple. Calibre stores metadata in its own database. It only updates the metadata in the actual file when one of two things happens -- either (a) you do a "save to disk" operation, or (b) you do a "send to device" operation. In either case, what is saved/sent is the original file with its metadata updated to match what the database knows it should be. So, if you copied the pdf files via some other method that update of the meta-data would be skipped.
- There are some known bugs in Calibre's support for pdf metadata. Most of the ones I've seen discussed here caused hangs or crashes, but it would not be too surprising to find incorrect meta-data as another possibility. If the previous item is not the solution to your problem, you've probably encountered one of these bugs. In that case, you should report it via the "ticket" system at the calibre website.
Hope this helps.
Xenophon