well I tried with GW=67577kg and full manual SPLRs, the acft still climbs ate 2000fpm past FL100... so SPLRS is not your issue.
You said you load with TOPCAT? can you try without that? you load the acft from aircraft menu again. Then you manually change the load of the acft to around 65000kg. I heard there were issues with topcat and my soft already...
JL