Oh was this a fun one to hunt down.
Build something that uses IPIVR/IPQM on the CRS system.
Build a call flow that transfers some callers from the CRS/IPIVR/IPQM to an external IVR.
Have those transfers cross a QSIG trunk.
If a “connected number” display IE comes back in response to one of those transfers, your CTI ports on the CRS system will eventually permanently die. You won’t get them back until you reset the CRS engine.
Sound bad? Well it’s true. Turn off connected number display from the far side of the QSIG link and all will be fine.
Bug ID forthrcoming soon.