I’d try different battery batch / different battery company to check if it’s mouse issue or the battery.

I tried it with the battery that came in the box, but it still stays at the same level and shows half charge.

I’d check it on BT mode and see what’s system indicator will tell about the battery level, because Synapse can be buggy sometimes here.

i ma facing the same issuer and it says my mouse is out of warranty. My previous mouse ran 3 years on same battery and still runs. I have 3 batteries in a month and still the issue is persistent.

i hope someone reads this thread and actually solve the problem else this would be my last razer