Transformation Failed Problems generally indicate a problem with the configuration or the formatting of the commands sent to the device to implement them. There was a recent development enhancement pushed out to Mist that now identifies configuration issues that would cause critical issues and prevents them from being committed.

For this particular error or situation, an attempt to modify the BGP config was done.

Unable to push config with the following error: Transformation Failed Problems: 1: Error: Traffic-steering for all_wans has no valid path

The solution is to correct the misconfiguration.

In double checking the configuration for this particular scenario, there was an overlapping variable in the site config that was missed causing the wan interface to go down.

Double check the configuration being pushed to ensure all configuration is appropriate and correct.