I’ve seen it before too. I’m thinking that restarting the computer clears the caches and the warning. It it repeats itself open a support request like Boshra said. Do you know how to get the log for the build?
it is in this folder
Windows : C:\Users{User}\AppData\Roaming\watchfacestudio\dump\main.log
or
macOS : /Users/User Name/Library/Application Support/watchfacestudio/dump/main
Ron
Samsung Developer Relations