I think I agree with PIX for point 2. I have also experienced with this.
THe TCH Blocking occured but the traffic was very small. Then I checked the GPRS PDCH Traffic, then i saw there are GPRS traffic. Because in the counter, GPRS traffic is not counted as voice traffic so the traffic show very small although in BSC database setting the GPRS is down grade first, but this problem still occured. Then I discuss with customer to disable GPRS in the cell that indicated problem to see the performance, then resulted in normal condition.