Is close call enabled when you hear the beeping? What does the screen say when the scanner beeps? Too many unknowns to know for sure but for me personally, the key beep is the first thing I disable whenever I get a radio: Menu > Settings >Adjust Key Beep> Off
The only time time I know that the 536 beeps are with an error, that the SD card have a problem to store or retrive data or something similar.
The display says nothing at that exact moment, but perhaps you don't have eyes on it right then and only hear the beep?