I found this bug after just opening the standalone gui tool for Oracle webcache, luckily the fix was easy just a reregister.
Unable to fetch or parse webcache.xml from : Authentication failed: password mismatch.
Unable to generate or transfer webcache.xml from : Authentication failed: password mismatch.
The fix was to simply reregister the component.
$ORACLE_INSTANCE/bin/opmnctl updatecomponentregistration –componentName <mywebcachename>
$ORACLE_INSTANCE/bin/opmnctl updatecomponentregistration -componentName webcache1
Also found that you may need to bounce the Middleware control to have it stop erroring after this occurs.