I try to customize a Custom the Form of SharePoint List with PowerApps. The List contains the standard Title (Required) Field and a People (Person or Group) Field. The Field allows selection of "People and Groups".
The PowerApps Form saved successfully.
If I try to add a New Item, PowerApps shows the Error-Message "There was a problem saving your changes. The data source may be invalid". The whole Form values were reset.
Is there a known Problem with People-Field for Groups?
Sorry for the late response. Maybe you figured out the issue by now. But I ran into this same problem. I had to reset the form back to default SharePoint view and then customize Form with PowerApps again. To use the default form:
Click the gear button on the top right > List settings > Form settings> choose Use the default SharePoint form > OK.
Note: I also clicked on the Delete custom form link under the secon radio button option.
After I did that, I no longer ran into the data source and Title field issue.