When you run vxrecover -o force, it recovers only one subvolume and it cannot detect that the rest of the volume needs recovery.

When you run the vxassist mirror command, you run the vxplex attcommand serially on each subvolume. If the failure happens before you start the attachoperation (need to mark the concerned plex as the attach operation is in progress), vxrecover will not redo the attach operation because it cannot find any record of the attach operation in progress.