mouse acts weird on Windows 10 when connected to extern monitor

You probably should ask in the Microsoft support site.

lethargos wrote:

I have this weird problem whenever I connect my macbook pro to an external monitor. I'm running Windows 10 Pro. The problem occurs only when I close the laptop's lid. The mouse starts acting up, it applies clicks randomly. Perphaps even stranger is that it stops doing it after 5 minutes or so. On the other hand, if the lid is open and I work on both screens, then it acts normally.

In quite a few cases, this is a symptom of your battery swelling up. This causes the built-in trackpad to generate spurious clicks. Check the level of you trackpad and the cycle count of the battery. Also check System Report -> Power for any thing out of the ordinary.

Disconnect the USB mouse, close the lid, reconnect the USB mouse and test. If you have a BT mouse, test it if possible.