partial measure in the middle of a polyphonic score

[Federico Bruni]

I'm trying to put a partial measure in the middle of a score using \set
Timing.measurePosition

This works fine in a single voice score.
I have problems with a polyphonic score: if I place the command above in
second voice only, it works fine; if I place it in both voices, I get a
warning (barcheck failed).

See attached minimal example...

Maybe I should change the context (Timing > ?)?
I made a few tries, but no success..

Thanks,
Federico

measurePosition.ly
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