A user reported a strange issue - suddenly she is unable to click on any drop-down menus. The menu would open for a fraction of a second and then immediately close making it impossible to select anything. Google Chrome and Microsoft Edge are affected. Connecting another mouse makes no difference (tried wired and wireless mice).
I was providing support remotely via TeamViewer and immediately noticed another issue - I could not operate the mouse via TeamViewer at all, unless I enabled TeamViewer's "Disable Remote Input" option.
After a bit of digging, I found that there were 2 entries for mice in Device Manager under Mice and other pointing devices. I tried to uninstall them both, but after scanning for hardware changes, both would immediately get reinstalled. The user was swearing that there was only one mouse connected and apart from the keyboard nothing else was plugged into USB ports. After insisting for the user to go around the PC and closely inspect every single port, she finally found a "very small" dongle plugged into one of the USB ports, which apparently was there "for ages". No idea why it started causing issues that particular morning, but removing the dongle immediately resolved the issue.
Dell Optiplex 7010 PC
Windows 10 Pro