Which clock mode? For me it seems that after the clock is transferred from the circle display to the main display, so when the meter is in standby, the clock is less accurate. But if the meter is kept active, during measurement, the circle clock is accurate.
Also the clock in my meter is accurate when the meter is switched off. After powering up, the time is consistent.
So it seems that clock might run a bit slow only in the standby mode, where the clock digits are presented on the main display.
Did not get a response from neo2001 if his unit is silent, so no noise, after setting the display brightness to maximum while using the speaker function.