When you statically register a user SVC using the IEASVCxx parmlib member for MAR 8.6 or later, you do not need to define the SYMDEF statement (&YKSVCNO system symbol) in the IEASYMxx parmlib member.
Disable (comment out) the SYMDEF statement in the IEASYMxx parmlib member, as shown below.
/* SYMDEF(&YKSVCNO='SVC-number') */