One of the sort-of false-negatives. To solve them:

Right-click the error-message, this will take you to the openpage-activity or microflowcall-activity.

Click on edit, to take you to the parameter-values to pass to the page/flow. Then Studio will likely find the values and without anything visually changing, you can now click ok and refresh, and you have one less error.

Repeat for each errormessage