NAD C356BEE Relay clicks

NAD C356BEE integrated amplifier.

if it is turned off for a long time (1 hour....for example) from the outlet or rear switch when I turn it on, the relay RL311 on tone board clicks at a frequency of 2 times per second for about 20 seconds, the orange led "standby" flash too.
Amplifier cannot be turned on at this time. After 20...25 seconds Amplifier is on standby mode and can power on normally.

If it is in sleep mode all time then it turns on normally.
When plugged into an outlet.