Got this mouse in about June (2020) and it has been fantastic! But as of about an hour and a half ago, both of the thumb buttons (Mouse button 4 & 5) both activate together. Basically, if I click MB4, it activates MB4 and MB5. Both click without an issue, but they both send each others signals to any program I'm in. I've already reset the mouse' firmware twice, no fix. Should still be under warranty, but it seems like a software issue. Anyone have any suggestions before I just send it back for a new one?