Issue Opening Main Form Designer in Version 1.3.74 1.3.7760.20546

I have cloned the latest version of the code and was able to compile and run the application. The issue i have is when i try to open the designer of form MainV2.cs , it shows MissingMethodException. Please find attached screenshot of the same.

Please advice on further steps.

Update –

Based on the 1st screenshot i tried opening the designer file for myButton.cs under Extlibs->Winforms->MissionPlanner.Controls and it is also throwing an error as shown in the 2nd screenshot.

It looks like myButton.cs is causing the issue when i try top open the Main form designer.

Please advise as i am stuck and need to move ahead on this and i need to work on the latest version of the code.