After erasing the font cache and regenerating LM was doing it right
again.
Helvetica did not, but maybe I made a mistake in
\definefontfamily
[helvetica]
[ss]
[Helvetica]
[tf=style:Regular,
bf=style:Bold,
it=style:Oblique,
bi=style:Bold Oblique]
Does it work when you remove the manual assignments to tf, it, etc. or
when you use lowercase names (without spaces), e.g. "bi=boldoblique" (or
"bi=bolditalic").