National roaming -PS RAB degradtion

[luganomu]

We are observing PS RAB degradation soon after National roaming activation with competitor. Let say local Operator A and B

The activation is Customer for operator B to roam to Operator A. once activation is done during Maintenance window PS RAB ( R99 , HSUPA/EUL and HSDPA rab degrades ) and the failure reason is due pmNoFailedAfterAdm - we also check PDP degrade sometime

PLease assist what could be the problem

PS core : HUAWEI all operator
RAN: E/// all operator

CS core huawei all operator