"What is that crud? Glue? Oxidation? Is it possible to remove?" it can be easily removed with a cotton swab and isopropyl alcohol.
"Note that Denon often uses JVC TRS-1005, which droops more that TRS-1007" I've never seen a comparison of JVC TRS-1005 vs TRS-1007. Maybe you have a link?
Normally that can clean most anything for me but a rigorous cleaning resulted in no change. I am considering trying out a Magic Eraser bar but am nervous about it. It hasn't been a good day for me as far as styli go so I am likely going to leave it alone. My concern is that it is a poor glue job and if I dissolve or force it off somehow the diamond will fall off.
I did find that a stylus I thought I cleaned was still dirty. I wasn't 100% happy with the measurement results and perhaps this helps explain why. Perhaps. The dirt was really caked-on, likely from long-time storage in suboptimal conditions. I bought it from Japan and it seems that they have a big storage problem over there as A LOT of used cartridges up for auction are corroded as hell. That makes me worried about the internals. I am thinking most of the good stuff was picked over the last few years. I am much more wary these days.
Managed to get rid of most of the dirt. A re-do is on the docket for this week. If there is no change perhaps the uneven diamond cut throws it off balance and is to blame.
Also I am confident there are measurements of the TRS-1007 on this site. Do a search. Check the Test records, Fun with vinyl measurements, or MM MC MI threads.