We have the same problem here, BSS B10 but on all BSCc
We opened a ticket with TAC when we activated SIM prepaid where most of these SIM do not have access to GPRS, high UL TBF failures suddendly raised.
Still no answers but according to NPO support, counters are not properly reported in NPO.
We noticed ous customers are not impacted with this, it is just counters.
Last week, we reset a BSC and UL_DL TBF failures raised down of 10 per cent, this is the magic of ALU !
hope that help, keep us updated on your findings.