both these two features, udid_mismatch and clone_disk, are designed to assist system admin/users to better manage their storages and to save guard user data preventing data corruption. To achieve so VexVM uses a few IDs to identify each physical storage unit. From time to time, for various reasons, users need to clone storage devices and some times present both the original set of storage and their closes to the same system. Therefore to better manage the storage devices and avoid data corruption, both close_disk and udid_mismatch flags are introduced.
For more info regarding these two rea the articles below
https://sort.veritas.com/public/documents/sfha/6.2/aix/productguides/html/sf_admin/ch03s11.htm
https://sort.veritas.com/public/documents/sfha/6.0/linux/productguides/html/sfha_solutions_tshoot/ch08s01.htm
https://www.veritas.com/support/en_US/article.100038560
prior performing any maintence, make sure you have all user data backed up, collect a set of newVRTSexplorer/DataCollector output, apply the latest Veritas patches.