NB: Did not recur after restart.
Having landed MH9, I went into configuration to confirm one setting.
Upon Continue, I gave my mouse a wiggle and ... to my amazement ... bird lifted off.
I repeated this cycle a number of times, with and without going into Configuration.
Landing and wiggling responded as expected.
Landing, going into settings, returning ... mouse wiggle would trigger Collective Raise.
Restarted the game, went into same slot on same server with same bird and all good.
p.s. perhaps not related, but in the same session: AutoHover failed to maintain altitude.
Addendum: this reoccured last night; TAW US public server (very reliable); one of many, many flights. Entered helo, started engines, turned away to do something else, turned back, gave mouse a slight wig-wag and watched craft rise into the air.