Mouse issues: Unable to grab cursor

I've recently started loosing control of my mouse left-click. Symptoms:

1. Unable to left click anywhere
2. Mouse cursor usually gets stuck on the insert cursor shape
3. running xkill will error with "unable to grab mouse cursor`

Suspected cause: This usually starts when I've been alt-tabbing to swap windows too... aggressively. Maybe I'm mistyping a hotkey?

Debug info: I have found that I can temporarily fix the issue by right-clicking the application icon in the launcher. I will then have my mouse back until I swap windows again (whether with the mouse or alt-tabbing)

Environment: 16.04LTS

How can I fix? Thanks.

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