Win 10 Pro on Dell Optiplex XE with 32GB Ram, SSD hard drive. Customer updated to 1903, newest upgrade. After that the mouse is screwy. It can happen in many different ways but it’s not reproducible every time. Here’s how he describes some of the symptoms:
On Google Calendar he will be on the October page, click to go to November and instead it skips over to the December page.
He has Picasa up on his screen. His Gmail is open in a browser window beneath it. Clicking on a picture in Picasa opens an email.
He goes to write an email. Clicking on compose opens two compose windows instead of one.
In powerpoint, he clicks the X to exit and instead it goes to print.