Blackwidow V3 PRO percentage problem

I recently discovered a percentage problem with my keyboard. Idk when it started, but the keyboard’s percentage seemed to be stuck and after a while it lost 1%. It was stuck at 87%, now it’s 85% (it’s still charging). I tried to use it wirelessly for a while (when it was at 86%), the percentage dropped at 84%, but after I plugged it in, the keyboard charged until 86%. This shows that the cable is working and charging. I reinstalled all the drivers and softwares, even updated my keyboard, but to no avail. Now it’s stuck at 85%. Oh, I also put the cable in another usb port. Is the battery faulty or is it a hardware problem? Quite ironic, having a cable, but not being able to do much, but to prolong the keyboard’s life…. I’ve been using this keyboard for no more than half a year. Maybe 7 months, but no more…. Does anyone have any idea what may produce such a “phenomenon”?