Hi David, we reached out directly as well. I wanted to close the loop on your post here.
There are two possibilities that come to mind so far.
First, there is a Salesforce Release Update (formerly called a Critical Update) that may be relevant if you have started testing it, or have activated it. The update is called “Enable Secure Static Resources for Lightning Components.” Can you check and see whether this is enabled, or in ‘test mode?’ You’d be able to see if it’s in test mode by clicking the Get Started button. Be aware that you may not be able to disable this once you click the “Done” button.
Second, you may need to add the https://gateway-us.skuid.net domain to the Trusted Domains in Salesforce. You can do this by visiting the Session Settings page in Salesforce setup.