M19/orient spindle while spindle is running?

trying to mate orient spindle pins to the spindle drive with built-in orient function.

the drive is basically controlled with 3 signals: FWD, REV, ORI. they are level-sensitive. the ORI orient signal has priority over FWD/REV and is honored whether the spindle is rotating or not. while ORI is active the orient-complete ORC is output and spindle is locked. when ORI deasserted, the spindle returns to a previous state.

in linuxcnc (2.8.0pre1 from github) spindle.0.orient is reset to FALSE as soon as spindle.0.is-oriented is signaled, so i am OR'ing spindle.0.orient with spindle.0.locked before feeding to drive's ORI input.

this works unless spindle is rotating when M19 is issued. in this case spindle is stopped, spindle.0.orient is asserted for a brief moment and reset without waiting for is-oriented or signalling any error...

how is M19 supposed to work with the spindle running?

also, the documentation on M19 says: "Spindle orientation requires a quadrature encoder with an index to sense the spindle shaft position and direction of rotation.". i guess this means for use by whoever implements the orientation function?

yes, a fixed angle required by the toolchanger.
it was handled by M64/M65 before, i just thought it would be cleaner to use a standard dedicated M word... probably not a very good idea
thanks!