Tail-dropped packets on 30Gb AE while only ~8Gbps at max

Hi all,

I see lots of output drops on a 30g AE (consisting of three 10g interfaces). It's a 2 member EX4550 VC:

Model: ex4550-32f
Junos: 15.1R5.5

AE detail stats:

  Output errors:
    Carrier transitions: 44, Errors: 0, Drops: 127061556, MTU errors: 0, Resource errors: 0

Queue counters:       Queued packets  Transmitted packets      Dropped packets
  0                                0        8786218535053            126988388
  1                                0                    0                    0
  5                                0                    0                    0
  7                                0          29847977601                73168

Thing is, at max the interface is doing 'only' ~ 8Gbps. This is only at night. During the day (like now) it's only doing approx. 2G in and 2G out. And even than I got ~ 254 drops within a minute.

I understand tail-dropped means they're dropped because the buffer is full. But I really can't figure out why. At least looking at the bandwith, there's enough room.

One thing I just noticed, while checking when it appeared to have started: ~ 2016-12-29 01:36:04

That night, we replaced this stack with a new one which was installed with 15.1R5.5; (we did this to reduce downtime, as it's a core stack)

Also, from that moment on there's a huge increase of outbound traffic.. that concerns me ..

So one could think it's caused by the JunOS version?

Any insights would be appreciated!

[edit: added images]