when you remove device from a storage group, you have to add -unmap.  You can try put it back in the group and then remove it with -unmap or follow the goo'ol procedure of write disabling the device and unmaping it.
I have a metalun I need to shrink by one member but the vmax won't let me do any operations, including disolving, on the device becuase it thinks it's mapped to FA ports. I removed the dev from all masking views and storage groups but the symdev show output still shows it mapped. How do I shake it loose?  Thanks.  VMAX code is 5875     EMC:SYMCONFIGURE iCfgChgSessionStart Starting a local CfgChg session for SID 000192600394, symapi V7.2-1159 (1.0) ucode 5875 Establishing session with Local cfg srvr (000192600394)...Established.Session ID 3084544 (0x002f1100)SymConfigChange Define error in dfn 1:remove dev 05C0 from meta 05B8;The specified device must be unmapped or unmasked before the configuration change can be applied.Device 05B8 generated the failure Terminating session with configuration server.............Done.  Symdev show output:      Front Director Paths (12):{ -----------------------------------DIRECTOR PORT LUN ---------- ---- -------- ---------Type Num Sts VBUS TID SYMM Host-----------------------------------FA 07E:0 RW 000 00 057 N/AFA 08E:0 RW 000 00 06D N/AFA 09E:0 RW 000 00 06D N/AFA 10E:0 RW 000 00 057 N/AFA 07F:0 RW 000 00 056 N/AFA 08F:0 RW 000 00 056 N/AFA 09F:0 RW 000 00 056 N/AFA 10F:0 RW 000 00 056 N/AFA 07G:0 RW 000 00 056 N/AFA 08G:0 RW 000 00 056 N/AFA 09G:0 RW 000 00 056 N/AFA 10G:0 RW 000 00 056 N/A} 
Can not unmask device on vmax