My designer started to crash, even on clean projects. The error message is as follows:
System.Exception
Package failed updates, dependency or conflict validation
It looks like you are missing some packages, you need to look into Nuget and see what packages are missing. Or with NuGet you can restore all packages in the solution using the command line.
nuget restore YourSolution.sln
Or Reinstall all packages in ALL PROJECTS of the current solution:
Update-Package -Reinstall
Reinstall all packages in SPECIFIC PROJECT of the current solution
Update-Package -ProjectName 'YourProjectNameGoesHere' -Reinstall