It sounds like you need to replace the battery. Get a new fresh from the store brand name battery. Even if the battery low indicator is not blinking, I would suggest switching this out. Also, do not use rechargeable batteries.
Replace the battery with a brand new name brand, then reset your board. You can reset the board by taking the battery out and holding the power and function buttons at the same time for like 10 seconds I believe. I will double check that and edit if its different.