Today, I have many errors with uipath like image attached below. I edited variable only the application also was crashed 
As mentioned in the error message, restart your UiPath studio and also the computer as well. Then check again.
Is this the same process developed with the same version of UiPath studio?
yes, but errors occur too much, i can not do anything else then I deleted all multiple assign activity and use single assign activity only to resolve this issue.
Hi
Update all of the packages to the latest versions will resolve the issue, for that go to Design tab → Manage Packages → Project Dependencies and upgrade the package version
or
delete the project.json file and open the xaml file
or
reinstall the application and open the xaml file once
Cheers @ngocvk
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