You perfectly answered my questions 🙂
So let me rephrase :
1/ the MS1 canot be reached, unless it made a call before.
–> this is typical from MS that is not attached.
2/ there is a attach/detach parameter in ericsson
… is it set to YES or to NO ???
If it is yes, then the problem comes from the MSC/VLR : the IMSI detach timer is too early ! it is a specific timer from VLR, I’m not talking about the parameter you described, which is in the BSS.
Check that the VLR parameter is >> than the T3212.
What is the value of T3212 in your cells ?