Idle LACP ports on IRF linked switches

[Kenny_10_Bellys]

I look after a large campus network that just changed over to A-series switches from ancient Cisco kit.  We have a pair of IRF linked 12500's as our core switch, and there are 5 distribution layer switches linked to those.  Each area distribution switch is actually a pair of A5820X switches linked by 4 x 10Gb IRF links over fibre (the switches are in different buildings) so that they run as a single switch.  Each of these is in turn linked by 4 x 10Gb fibre links to the core (2 from each switch).  We are still connecting up all the fibres right now, and have hit a snag

On one IRF linked pair of 5820's I currently have 3 x 10Gb uplinks connected to the core (1 is awaiting a fibre link).  They are up and showing connected at each end, but only 2 of them are actually selected and passing data.  The single link on the master switch is up, but shows as being in a default and unselected state.  I tried shutting and reopening the bridge-agg interface for it, but that did nothing.  I even rebooted the switches making sure the master came back first, but no change.

Here's the config for the links.  There's nothing different to any of the dozens of other links which are happily working as normal, but on this one I have a single idle fibre...

Distribution Switch 2 (IRF linked 5820's)

interface Bridge-Aggregation1
 description *** Link to Core MAD enabled for IRF ***
 port link-type trunk
 port trunk permit vlan 1 99 106 820
 link-aggregation mode dynamic
 stp instance 0 port priority 0
 mad enable

Core Switch

interface Bridge-Aggregation12
 description Link_to_Dist_2

 port link-type trunk
 port trunk permit vlan 1 99 106 820
 link-aggregation mode dynamic

The dist switches are A5820x-28s running Comware 5.20 1110P05.  The core switches are A12508's running 5.20 1238P08.  Why would one fibre not be included in the agg group?  All are configured in an identical way, and the switch configs are identical to 4 other paired sets which all work properly.  The link is up, so its not fibre or SFP causing it to fail, it just sits idle.  Help?

[manuel.bitzi]

be paste the output for "disp link-aggregation v" from both switches and have a short look the the lof "disp logbuffer rev".

br

Manuel