I've seen this before on 8.5. QlikTech support found a bug in the plugin which was sorted in a later release of 8.5.
The bug we found was consistent across multiple computers, and seemed also to be due to conflicts with other plugins.
I suggest you try to Unistall other plugins, try If a clean install operating system has the error, and try to identify if another plugin causes this.
If its consistent across multiple installations, I would suggest you contact support.