Some depth gauges have both a low depth warning and a high depth warning. Getting beeps when you're plenty deep could be the high warning. My old one used to do that and it took a while to figure out what it was. I have similar issues with false or blank readings and my aftermarket Uniden is only a year old. I've found when I'm listed over surfing it doesn't like to read. Following in the wash of another boat it doesn't like to read either due to the bubbles I'm sure the signal is bouncing off. I know my puck is glued tight but even little air bubbles in the glue can cause problems from what I've heard.

I think a future upgrade will be one of the style with a thru hull eye.