Guix package: the daemon crashes while making an audio call

Hi, I have a problem with our Guix package - while making an audio call, the daemon crashes with the following message:

dring: ../src/pjsip-ua/sip_inv.c:246: pjsip_inv_dec_ref: Assertion `inv && inv->ref_cnt' failed.

Any idea what could be the cause? I suspect we have pjproject packaged badly, so it won't be reproducible with your version. I don't need a full answer, if you won't be able to tell me exactly what's wrong, just a hint would be good. The version is 20200124.