This issue occurs either due to a prior failed vSAN deployment or a previous vSAN configuration that did not get fully cleaned up.
Example: 1 of 3 cache devices on each host has a remaining partition on it. The host should have 3 Cache disks and 12 capacity disks configured to 3 separate disk groups, 1 cache and 4 capacity each. The example set in place has 2 separate disk groups, 1 cache and 6 capacity each.