Migration from SharePoint 2010 to SharePoint 2016, via SharePoint 2013 – Based on Native Approach.
(Assuming same for Migration from SharePoint 2013 to SharePoint 2016)
When workflow is opened in SharePoint Designer, it goes for crash screen as below.
Open SP Designer, such that go to: All Files >> Workflows >> target workflow.
Change assembly version from 14.0.0 to 16.0.0
Or for Migration from SharePoint 2013 to SharePoint 2016, change from 15.0.0 to 16.0.0
Save file, Check-in.
Now open workflow again. the crash screen, will not appear.
Also delete SharePoint Designer cache at following location.
C:\Users\UserName\AppData\Roaming\Microsoft\Web Server Extensions\Cache
C:\Users\your user name\AppData\Local\Microsoft\WebsiteCache