I defeat this problem by moving the dongle closer to the mouse, in my case, my keyboard has a USB port, but most dongle mice have a USB cable you can use to extend the dongle out.
It seems to use the 2.4 GHz wireless frequency, which is notoriously overcrowded with wifi, bluetooth and all manor of wireless connections. Any of these will lessen the stable connection length. So do you use other wireless devices in the area between your mouse and the PC?
If y'all seen my recent post about messing up my Arch install, I needed to reformat my PC. I never had problems with range because. The mouse connected better than my keyboard. Now my mouse is the thing part causing range problems. I tried connecting to different USB ports. Played around like heck with openrazer and different frontend software like Polychromatic. Still having a range issue.
I do have Bluetooth and Wifi setup on the computer, even though I use Ethernet. I'll tried shutting them off and see if it improves. Thanks!