Introduction:
Q. What does the Performance Service - Stats DB object conflicts check do?
A. The check verifies whether there are multiple Stats DB objects present on the vSAN datastore.
Q. What does it mean when it is in an error state?
A. Multiple Stats DB objects were found on the vSAN Datastore of the associated vSAN Cluster.
The related directories were renamed by appending a number to the directory name (e.g. "vsan.stats-1", "vsan.stats-2", "vsan.stats-3", "vsan.stats(1)", "vsan.stats(2)" etc. )
This is an issue because per vSAN Datastore there can be only one Stats DB Object (= Directory named ".vsan.stats" without any number appended).
Symptoms:
Warning in vSAN Health:

The Error details (when clicked on "Troubleshooting"), show one or more directories named "vsan.stats" with a number appended
Naming Examples: "vsan.stats-1", "vsan.stats-2", "vsan.stats-3", "vsan.stats(1)", "vsan.stats(2)"
Alert Examples from different Clusters:
Example A.):

Example B.): 
Via Datastore Browser: Multiple Folders named "vsan.stats" are shown
Examples from different Clusters:
Example A.):

Example B.):
Via SSH/Putty to any of the vSAN Hosts: Multiple Directories named "vsan.stats" are shown
Example:
You might observe: When trying to access one of the folders you get the error: "Operation failed! File [vsanDatastore] ########-####-####-######### was not found"
Example: