Respring when switching between calls

Anyone else get a respring when switching from one call, to another? I just did today, and it was weird because the first caller stayed on the line even after the apple logo came on the screen and it resprung. The second caller was dropped immediately.

iOS 7 B6 has been very stable for me up until this, and a soft respring last week while plugged into itunes not doing anything.

no resprings on B5.