Comp-head phrase clashes with its parents; question particles

Grammar Matrix
#1

I have a grammar for which the choices file specifies SVO word order (so, a head-comp phrase) as well as sentence-final question particles (so, a comp-head phrase).

The grammar doesn’t load and I don’t quite understand why. The error message is that the comp-head phrase clashes with its parents, and removing the HEAD comp constraint fixes that, but why is there a clash in the first place? None of the phrases parents say anything about HEAD, as far as I can see? I include both the addenda in mylang.tdl and the matrix types:

; comp-head-phrase requires things that are [ HEAD comp ].

comp-head-phrase := basic-head-1st-comp-phrase & head-final &
  [ SYNSEM.LOCAL.CAT.HEAD comp,
    HEAD-DTR.SYNSEM.LOCAL.CAT.HEAD +nv ].

basic-head-comp-phrase :+ [ SYNSEM [ LIGHT #light,
             LOCAL.CAT [ HC-LIGHT #light,
                         MC #mc ] ],
    HEAD-DTR.SYNSEM.LOCAL.CAT.MC #mc ].


basic-head-1st-comp-phrase := basic-head-comp-phrase &
  [ SYNSEM.LOCAL.CAT.VAL.COMPS #comps,
    HEAD-DTR.SYNSEM.LOCAL.CAT.VAL.COMPS < #synsem . #comps >,
    NON-HEAD-DTR.SYNSEM #synsem ].

basic-head-comp-phrase := binary-nonloc-phrase & head-compositional &
              binary-headed-phrase &
  [ SYNSEM phr-synsem-min &
           [ LOCAL.CAT [ WH [ OR < #or1, #or2 > ],
                         VAL [ SUBJ #subj,
                               SPEC #spec,
                               SPR #spr ],
                         POSTHEAD #ph,
                         HC-LIGHT #light ],
             MODIFIED #modified ],
    HEAD-DTR.SYNSEM [ LOCAL.CAT [ WH #or1,
                                  VAL [ SUBJ #subj,
                                        SPEC #spec,
                                        SPR #spr ],
                                  HC-LIGHT #light,
                                  POSTHEAD #ph ],
                      MODIFIED #modified ],
    NON-HEAD-DTR.SYNSEM canonical-synsem & [ LOCAL.CAT.WH #or2 ],
    C-CONT [ RELS.LIST < >, HCONS.LIST < >, ICONS.LIST < > ] ].

Does anyone have an idea? MC and LIGHT and HC-LIGHT are appropriate for any CAT…

#2

For some reason, this rule is specifying HEAD values for both mother & head daughter, and they are incompatible:

comp-head-phrase := basic-head-1st-comp-phrase & head-final &
[ SYNSEM.LOCAL.CAT.HEAD comp,
HEAD-DTR.SYNSEM.LOCAL.CAT.HEAD +nv ].

(The conflict with the parent is presumably with head-compositional, which identifies those HEAD values.)

#3

So, if a language has clause-final particles but subordinator-complementizers which go before the causal complement, that would not be possible to model via these HEAD constraints, would it? Would need other features (INIT?)

#4

Either different HEAD types for those, or an INIT feature. But INIT should work, because these are all things that only pick up one complement, right?