For all I know is that……
On both your scenariors means that you have a coverage problem.
You might be having an island site
SDCCH RF…happens before the allocation of the tch(still on sd) and the connection is lost, that increases your SDCCH RF LOSSES.
TCH RF…happens when on the tch you lose the connection ,may be due to coverage(during a call there is no other site/neighbour to hand to,to continue with call).This will increase your TCH RF LOSSES.
1.The one way to overcome this is to upgrade your TRX’s and SDCCH’s
2.or Decrease TRX,Tx power=reduce coverage.(RxLevMin)