I posted a reply earlier, but it didn’t go thru this firewall from hell.. so just a quick reply
1. your CSSR : does it include SDCCH for LU ? it is a weird choice. It should just include origin. and termin. calls, isn’t it ?
2. high nuber of LU : is there a site (from another operator ? or from the other side of your lac brder ?) which has been going down and up ? massive amount of people can switch from one lac to another one in this situation
3. when are the peaks in LU load ? all over the day ?
too much LUs can create SDCCH congestion, which might block the call setup… but that must be a lot of LU…