WLC 5508 intermittent loss of connectivity

Question

Hi.
I have a WLC 5508 connecting directly to a distribution switch (3850) via a layer 2 etherchannel trunk fibre link with LAG enabled on the WLC.
Whenever there is a loss of power to the server room where both devices are hosted & power later gets restored, the distribution switch & WLC lose Layer 2 & 3 connectivity. Connectivity only gets restored when the WLC is power cycled or the fibre cables connecting to its SFP ports are removed & plugged back in. When this is done connectivity is restored between them, APs associate etc. Once there is a loss of power to the room for whatsoever reason again, the loss of connectivity issue re-occurs.
Disabled the etherchannel at some point, using only a single fibre trunk link between them, but the issue persists.
Also check for interface errors, CRCs, etc on both ends but there are none.
Can anyone please advice me on what the issue is & what can be done to permanently resolve this?
Thanks in anticipation.
Ope.

Answer 1

Software version is 7.4.100.0
int gig1/0/5
  switchport mode trunk
  switchport trunk encapsulation dot1q
  channel-group 1 mode on
int gig1/0/6
switchport mode trunk
switchport trunk encapsulation dot1q
channel-group 1 mode on
Port setting on the switch is set to auto-negotiate. Port setting on the controller is "auto". The link has been negotiated (& always negotiates) to 1000Mbps full duplex on both ends.
Presently in transit with no way of connecting to the device, but I checked the duplex & speed settings on both devices which was appropriately negotiated. Also checked for interface error counters on the switch, there was none. Checked the WLC logs too, there were no logs on issues with the interfaces or auto-negotiation.