After RE switchover on Backup peer of ESI LAG, if child flaps, LACP doesn't return to expected Attached state, goes to Collecting distributing until AE is bounced. 

Expected output from downstream switch:

EX4400> show lacp interfaces | match perio
      xe-1/2/0                  Current   Fast periodic           Attached
      xe-1/2/1                  Current   Fast periodic Collecting distributing
      xe-0/2/0                  Current   Fast periodic Collecting distributing
      xe-0/2/1                  Current   Fast periodic           Attached

After RE switchover on Backup peer of ESI LAG, if child like xe-0/2/1 flaps, LACP doesn't return to expected Attached state:

EX4400> show lacp interfaces ae0

xe-1/2/0 Current Fast periodic Attached

xe-1/2/1 Current Fast periodic Collecting distributing

xe-0/2/0 Current Fast periodic Collecting distributing

xe-0/2/1 Current Fast periodic Collecting distributing

Flap of ae0 will prevent the condition from repeated until another RE switchover causes the error environment again.

This problem is reported under PR1938565 and fixed in 24.2R2-S5 and later releases