I would assume that SymmWin would not be able to change that bit with the volume mapped. I am surpsied that the validation succeeded.
I just ran a few simulations and it looks like SymmWin blocks removing the attribute from a mapped device but is allowing adding the attribute from a device. I have asked the KB article owner for clarification since our documentation for SE blocks both actions.
Below is from page 49 of the latest 7.6 version:
SCSI3_persist_reserv (persistent group reservation) - In Enginuity 5874 and lower, this attribute is disabled by default. In Enginuity 5875 and higher, this attribute is enabled by default. When running Solutions Enabler V7.5 with Enginuity 5876 Q42012SR and higher, you can set or clear the SCSI-3 persistence attribute only if the device is unmapped.
Well, that is a change I did not know about; so my previous response was incorrect.
Yes; it seems that you do need to unmap prior to changing this attribute.