As per the following forum entry if the definition of a Flow that is being used in a PowerApp is changed the PowerApp does not recognize the change until the Flow is disconnected and reconnected to the PowerApp.
The error that results from this scenario is not easy to diagnose so we should make improvements to the user experience in one of the following ways.
1. Automatically reconnect Flows with related PowerApps when the Flow is altered.
2. Display a warning message when Flows are altered that instructs the user on what PowerApps need to be serviced.
So many threads and "Bugs" reports on this. It's really a big issue right now.
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For everyone wich has this error, here a workaround.
This keeps you from changing it all across your application ;-)
As long as you use the Collection schema only on this Flow you will be fine. If you ClearCollect() the same collection also from another Flow then adjust this flow, so it returns the same schema and dataset, also and do the same steps as above. All the red warnings should dis-appear.
Was looking how to do this for a while, so though lets post this for the community.
Hope this helps.