APs (LAP1142N) are disconnecting after joining the WLC (5508)

Question

Hi,
We are having a problem at the school I'm working at. There are 133 APs located across campus.
They have been running for 3.5 years without any trouble.
Recently we have been having issues with APs disconnecting at random.
It started last week with just a couple. We got them running again, but later the same day new ones had disconnected.
This has continued with more APs and it looks like it happens at random and it is never the same one that disconnects.
We have a centralized support-unit that helps us with stuff like this, but they haven't come up with a solution, so I was hoping someone here had seen this behavior before.
Today at 7AM all the APs were running, but at the time of this post 6 of them have disconnected.
AP (130 of them):
Product ID: AIR-LAP1142N-E-K9
Version ID: V01
Software Version: 7.4.100.0
Boot version: 12.4.18.3
IOS: 15.2(2)JB$
Country Code: Norway (NO)
Regulatory domains: 802.11bg:-E    802.11a:-E
Controller:
Cisco 5508 Wireless Controller
Firmware: 7.4.100.0
Recovery version: 6.0.182.0
Temp is running at 35C
Memory at a stable 50%
Cores 0%/2%, 4%/2%, 3%/2%, 4%/1%, 3%/3%, 5%/2%, 0%/1%, 0%/1%, 0%/1%, 0%/1%
Only using 4 of the ports on the controller 1-4
Some of the error-messages I have located on the different APs that have disconnected:
Layer 3 discovery request not received on management VLAN
Lwapp discovery request rejected
Just give me a shout if any other information is needed.
- Hille

Answer 1

You may be facing this bug CSCud97983
https://tools.cisco.com/bugsearch/bug/CSCud97983
Here are some more information about bugs we experienced with this 7.4 code
http://mrncciew.com/2013/02/10/day-0-with-wlc-7-4-code/
7.4MR2 (7.4.111.x) is available (pre-release image) if you want latest bug fixed image. This is specially if you are using wireless guest service & having apple iOS 7 devices.
https://supportforums.cisco.com/docs/DOC-37334
HTH
Rasika
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