Non clickable small icon keeps appearing at the end of the Dock

Hi everyone, I run into this issue pretty regularly, I am currently on Mac OS 11.6 (M1 MBA) but it keeps happening since the early version of Big Sur : a very small, non clickable icon keeps appearing at the end of the Dock. I can move it by moving the apps around it. It's often the Firefox icon, but it can sometimes be Messages or WhatsApp.

Quitting or launching the corresponding app doesn't do anything, neither does emptying the system cache.

A simple restart of the laptop gets rid of it, but it will eventually come back, sometime after a few hours, sometimes after a few days.

Would there be a command that could turn into an Apple Script that could help me erase it without restarting the computer ?

Thanks, have a nice day