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[LukaszE]

I have problem with all interfaces regularly detaching from LACP aggregation.

I have two DGS-1510-XX  physical stacks (mix of 1510-52X & 1510-28X switches in each) connected with 2x10Gbit link with LACP configured.
It is direct  optical (MM)  link between 2 racks, just  2 pairs of transceivers and ~10m of fiber patchcords, no additional hardware in the way.
Once 1-3 days both interfaces from LACP aggregations are in almost the same moment detached  from aggregation and after several seconds re-attached.
In result whole LACP aggregation goes down and up. (Than - I have STP on this link - it causes STP tree rebuild)
Whole time all physical interfaces in LACP stay up, I see no errors etc. on interfaces)
Problem occurs on different time, but ALWAYS about 37 seconds after full hour (!)

One example (from both stacks' perspective it looks almost identical):

2021-03-22T14:00:37+01:00 stack1 NOTICE: Topology changed (Instance:0, eth1/0/49, MAC: [...])
2021-03-22T14:00:37+01:00 stack1 INFO: eth2/0/26 detach from Link Aggregation Group 1.
2021-03-22T14:00:37+01:00 stack1 INFO: eth1/0/50 detach from Link Aggregation Group 1.
2021-03-22T14:00:37+01:00 stack1 INFO: Link Aggregation Group 1 link down.
2021-03-22T14:00:38+01:00 stack1 NOTICE: Topology changed (Instance:0, eth1/0/49, MAC: [...])
2021-03-22T14:00:42+01:00 stack1 INFO: eth1/0/50 attach to Link Aggregation Group 1.
2021-03-22T14:00:42+01:00 stack1 INFO: Link Aggregation Group 1 link up.
2021-03-22T14:00:42+01:00 stack1 INFO: eth2/0/26 attach to Link Aggregation Group 1.
2021-03-22T14:00:42+01:00 stack1 INFO: Spanning Tree port role change (Instance:0, Port-channel1) DisabledPort->DesignatedPort
[...]

I tried configuring slow and fast lacp rate (the same on both ends) - it did not change anything.
Bandwith utilization of links is very low (below 10%), I did not observe any traffic bursts in these moments.

Both stacks run latest firmware (1.70.012)
Normally LACP show both physical links as bundled:

switch1# show channel-group channel 1 detail
[...]
Channel Group 1
  Member Ports: 2, Maxports = 8, Protocol: LACP
  Description:
                       LACP         Port       Port
  Port          Flags  State        Priority   Number
  ---------------------------------------------------
  eth1/0/50     FA     bndl         32768      50 
  eth2/0/26     FA     bndl         32768      90 

LACP link is configured as vlan trunk:

interface ethernet 1/0/50
 channel-group 1 mode active
!
interface ethernet 2/0/26
 channel-group 1 mode active
!
[...]
interface port-channel 1
 spanning-tree cost 1
 spanning-tree portfast disable
 switchport mode trunk
 switchport trunk native vlan XXXX
 switchport trunk native vlan tag
!

Does anyone have any ideas ? (The only solution I currently have is to disable LACP on this aggregation...)