A simple workaround is as follows:
The workaround code is don't work properly...
Try manipulation1: Enter some value into ParameterFive_Edit and click by mouse outside SandBox GUI. You will see one MessageBox("No such file!"). Everything work fine, but now click MessageBox "OK" button and move mouse. Do you see that mouses modifier in wrong mode? Do you see blue selection rectangle. If you will try again and again, you can paint very nice picture. See attachment.
Also, you can see one more cursor bug: After manipulation1, enter some value, press "enter" (to confirm new value) and press "enter" to close MessageBox: Do you see Processing Cursor ( blue-green running circle )?