I am seeing the same experience, not just when the app is played as an end user, but also in design mode.
It's almost like the Salesforce connector needs to 'warm up', before being used. I experience the connections issues (which are false, because everything actually works), if I close the browser as a user or from design mode, then re-open, the errors are completely gone.
From a user perspective, it's obviously irritating & confusing that they see this error pop up on their first visit to the app each day. We can't really deliver useful business apps to users whilst they receive this error, even though the connections are actually working ok.
At the very least, it would be nice as designers to be able to supress/hide these error ribbons but we can't, however that would only gloss over the fact that there's a clear functional issue here that needs resolving.
The error is completely random. I have tried numerous things to try and recreate. Its more of an annoyance to the users as they believe the application is broken because of the error.
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