DD6300 fan speed increases every day for a short period of time

Hello,

I have a DD6300 (version 7.7.4.0-1017976),
on which every afternoon around 15:45 the fan speed increases for 1 - 2 minutes. However, nothing has changed in the room environment and the cabinet is air conditioned.

Is there anything that can be configured? Has anyone had this problem?

Via CLI I could find out that the temperature (environment, drive IO) also rises for the moment.

7 o'clock in the morning:
Enclosure 1
Fans
Description Level Status
----------- ----- ------
FAN 0A low OK
FAN 0B low OK
FAN 1A low OK
FAN 1B low OK
FAN 2A low OK
FAN 2B low OK
FAN 3A low OK
FAN 3B low OK
FAN 4A low OK
FAN 4B low OK
FAN 5A low OK
FAN 5B low OK
----------- ----- ------
Temperature
Description C/F Status
----------------------- ------- ------
Ambient Temperature 19/66 OK
SP Temperature 27/81 OK
MP Temperature 19/66 OK
CPU0 Temp Relative -45/-49 OK
CPU1 Temp Relative -48/-54 OK
Hottest HDD Temperature 28/82 OK
Drive IO Temperature 42/108 OK
DIMM Bank0 Temperature 28/82 OK
DIMM Bank1 Temperature 28/82 OK
DIMM Bank2 Temperature 28/82 OK
DIMM Bank3 Temperature 28/82 OK
----------------------- ------- ------

15:45 in the afternoon, the speed goes up:
Enclosure 1
Fans
Description Level Status
----------- ----- ------
FAN 0A high OK
FAN 0B high OK
FAN 1A low OK
FAN 1B low OK
FAN 2A low OK
FAN 2B low OK
FAN 3A low OK
FAN 3B low OK
FAN 4A low OK
FAN 4B low OK
FAN 5A low OK
FAN 5B low OK
----------- ----- ------
Temperature
Description C/F Status
----------------------- ------- ------
Ambient Temperature 19/66 OK
SP Temperature 27/81 OK
MP Temperature 19/66 OK
CPU0 Temp Relative -46/-51 OK
CPU1 Temp Relative -48/-54 OK
Hottest HDD Temperature 28/82 OK
Drive IO Temperature 42/108 OK
DIMM Bank0 Temperature 28/82 OK
DIMM Bank1 Temperature 28/82 OK
DIMM Bank2 Temperature 28/82 OK
DIMM Bank3 Temperature 28/82 OK
----------------------- ------- ------

From about 15:47 the fan is down again.
Enclosure 1
Fans
Description Level Status
----------- ----- ------
FAN 0A low OK
FAN 0B low OK
FAN 1A low OK
FAN 1B low OK
FAN 2A low OK
FAN 2B low OK
FAN 3A low OK
FAN 3B low OK
FAN 4A low OK
FAN 4B low OK
FAN 5A low OK
FAN 5B low OK
----------- ----- ------
Temperature
Description C/F Status
----------------------- ------- ------
Ambient Temperature 20/68 OK
SP Temperature 27/81 OK
MP Temperature 20/68 OK
CPU0 Temp Relative -45/-49 OK
CPU1 Temp Relative -48/-54 OK
Hottest HDD Temperature 28/82 OK
Drive IO Temperature 42/108 OK
DIMM Bank0 Temperature 28/82 OK
DIMM Bank1 Temperature 28/82 OK
DIMM Bank2 Temperature 28/82 OK
DIMM Bank3 Temperature 28/82 OK
----------------------- ------- ------