Ironically, after several days, I'm now able to have pull-down price wheel on price, not just other fields. Unless IB modified from their end, which is possible, also possible that a Windows upgrade fixed it. HOWEVER, each time I re-start IB, 10.12.2H does NOT retain the font sizes for boardwatch, nor BookTrader. Every morning must change from 45 to 24 font size. Again, in 15+ years, never had that problem.
Correction: Above was on my notebook computer, but the same IB version, the BookTrader does NOT permit pull-down price wheel. Very odd -- and very disappointing.