I have ESC's that do that also. They don't have an option to not beep when there is no input signal to them.
Apparently on version 3.3.3 the output was not being controlled by the safety switch so you didn't here the beeps. Now that this issue has been corrected you have beeps.
This is just the ESC's telling you that there is no input signal to them and they are not happy. Maybe there is an option to make them happy with your flavor of ESC.