I uploaded 3 files to OPUS today, 2 to OPUS-RS and 1 to OPUS-S. The two RS files processed correctly, but the S file used the wrong antenna. The first time I thought I somehow goofed (thought I couldn't figure out how, since I specified Trimble and OPUS used Ashtech), so I sent it again. Same result. I tried selecting a different antenna and then selecting the correct antenna, same result. The antenna goof shows up pretty much immediately on the "Upload successful" page:
The page before I hit the "Upload to Static" button:

And the "Upload successful" page:

Something on my end, a known OPUS problem, or ??
Go to options page and clear anything it might be remembering about you, then submit.
If that does not work, contact NGS and describe the problem. They can usually fix such hang-ups.
Paul in PA
I just tried it with a couple of my older files. On the first one I specified the normal antenna that I use and on the second I specified your antenna, it both cases the upload successful page showed the antenna I specified. I used rinex files rather than native trimble files.
Is the ashtech antenna one that you've used in a previous session? Or could it be reading it from your file during the conversion?
I launched a different browser and tried again, that time it worked. I also used a different email address, so I don't know if it was the browser or the address that worked around the problem.
I think Paul may be on to something with the options thing, but I don't know how to get rid of it. Just selecting something different didn't seem to work.
I recall the old OPUS page having a "store profile" option, which would retain the same antenna and some other settings between sessions. I've used it in the past, but it's been years since I've used an Ashtech Whopper.
Most browsers store some info in them and reuse the data rather than creating a new page. Maybe flushing the history/cookies will help. Just a possible idea.
Found it. Apparently I had set my profile to use an Ashtech Whopper more recently, probably while processing some CORS data. Once I reset that, everything started working as expected again.
In other words, User Error.