You should go and delete the views that you modified directly.

It is a very common error when you mix Views manually edited and new modules.

Other option is verfy in your code the xml reference mentionesd in your code (searching the chain "issue_count" in your addons path(s)

BTW, if you don put your code or all the conext of the error it is near to impossible help you, i can only share with you what the error means.

"You are inheriting a view who doesn't have the field that you take as pivote to show some other new field."

But BTW if you share with us revision of your code , and the modules you have installed is really more easy detect the problem.