Ancient PDB files
Back in the days of MobiPocket on the Palm, I got a bunch of files, including a free book from Baen. They were stored in pdb format (which is really just a compressed container, iirc). Calibre can read these, but, in the process of converting them into modern eBooks, I've run into some that come out with all the html tags visible. But since they're not "html" files any more, I can't re-convert them and have all the tags properly interpreted. At least not in any way that's obvious to me.
What am I missing?