No audio signal from region after pitch shift?

This is an issue that I’ve had since I started using Ardour about a year or two ago, but is not too serious since restarting Ardour fixes the issue. Figured I’d ask about it anyways, since it’s annoying.

Sometimes when I pitch shift an audio region in the editor (via Alt+8 or Region>Edit>Pitch Shift), after the transpose that particular region doesn’t output any sound. Other regions in the same track that were not pitchshifted are unaffected by this, with output as normal. It is just the pitchshifted regions that suddenly go mute. Restarting Ardour fixes it: the sample outputs the pitchshifted signal upon restart.

The pitch shift parameters don’t seem to make any difference here: when I face the issue, I faced it regardless of the semitones/octaves/cents shifted, and whether formants are preserved or not.

Any ideas why this happens?

[I’m running Ardour 6.9.0, Intel 64-bit via JACK (qjackctl, jackd v. 0.125.0rc1), on AVLinux-MXE.]

I use for pitch shifting graillon 2.
https://www.auburnsounds.com/products/Graillon.html

You can try it maybe.