2000 AP with strange ping results

Our monitorying software pings our APs every 30 seconds. One of our 2000 APs has had an issue where at night, the ping times go from a nomal 1ms up to 50 or 100ms for a few hours and then back to 1ms all day. I thought we were having a cable issue so I climbed the tower and replaced both the cable feeding the AP and put the AP into a different switch up there.  Problem did not go away. So it looks like it might be in the AP. The two other 2000 APs on the tower (and attached to the same switch) do not experience this issue.  Here is a 2-day graph pf ping times to the AP. This pattern repeats with pings increasing around midnight and then getting better around 5am.

Thoughts on the cause?  Am I having a hardware failure?

Device replaying on ICMP is lowerst priority in the system. If AP is busy with other activities (serving high number of SMs with relatively hig trafffic or browsing AP web interface), dely in reply might be observed. It is by design - customer's traffic is our main concern.

Isn't that AP more busy than 2 others?

It is not any more busy than the other two up there with it and the time of day ping times are the highest (3:00 am) is the time of day that traffic is the lowest. On very high traffic times (and 100% download utilization), we will see a little uptick in ping times (up to ~5ms) but nothing like the 50ms we see on this one.

What else is on this tower, or very near to this tower that may broadcast any type of RF? And... are you seeing anything weird with Ethernet statistics? The set timing seems as though something is coming up during these hours and causing an issue. 

I thought the same exact thing. The tower has some low power FM (under 300 watts) and UHF TV. We originally were feeding this switch with a 100' double shielded Ethernet from the bottom (in a metal conduit) so we swapped out to a 3' double shielded Ethernet from the fiber fed switch (Netonix) at the very top of the tower next to the radios. We now have 3 2000 APs and a UBNT AC AP all fed from this same switch - all with ~3' double shielded cables. This particular AP is the only one of the 4 that displays this issue. It started up about a week ago during a decent snow storm and has returned every night since then. Sometimes, it abrubtly ends in the morning. Some days it slowly gets better throughout the day before getting worse again at night.

Starting to sound like a temperature issue, which I am sure has crossed your mind as well. 

But still sounds like a hardware issue. If temp is having an effect on one AP but not the other two right next to it and this just cropped up, something seems to have happened to the hardware. I do have a spare but I'm trying to rule out everything else before I swap a radio at the very tip of my 100' tower. Not an easy task...

Yes, a temperature issue related to that particular unit. I have worked with Motorola systems for 20 years and seen this many times. 5 repeaters in a shack and one goes nuts with cold swings or hot swings while others work fine. 

Well, we have an ice storm followed by a high wind and blizzard warning coming in tomorrow so this should make for a fun few days even without this issue... Late in the week I may be able to get up the tower and replace with a spare and see what happens. If it fixes it, I'll try to use the Cambium 3 year warranty - even though I have no purchase info for that radio... At least the 2000 is less than 3 years old so it has to be covered!