900MHz OFDM Power level degradation after rain

Hi.  As our fleet of 900MHz OFDM CPE's are ageing, I am noticing more than normal power level fluxuations after rain.  Sometiimes the power levels recover on their own and sometimes it requires a truck roll to swap the CPE.  We are using the Cambium brand 12dBi yagis.  We had a record amout of rain here in the Chicago area this year and I realize wet leaves will affect power level.  Has anyone else noticed an issue with yagi's taking on water and affecting power level?

The small plastic caps on each tip of the yagi elements often come back missing.  If water collects in those tubes, will the power level be affected?  Why do those caps break / fall off?

Are the KP Performance Yagis that much better?  

I have not heard this before... when you "swap the CPE", are you changing both the radio and the antenna? Have you tried changing only the antenna?

I can send you guys a new antenna and attempt to get one back from you that's showing this behavior if you'd like. Maybe we can determine what's happening here.

We will normally swap both SM + Yagi since we have them all assembled ahead of time.  I asked our guys to attempt to swap one piece at a time @ the next service call.  Thanks Matt.

Follow up:

One of our guys tested a yagi that had come back missing a few end caps.  These fall out easily and most come back to us missing at least one.  

He poured water into the tube as it would while being mounted and it taking on rain.  He immediately saw a 10dB drop in power level.  I assume Cambium could reproduce this in house and take steps to improve the product.  

I guess part of our reconditioning process will be to take caps that face the ground and glue them into missing tubes that will face the sky.  

This has cost us quite a headache that could have been prevented.

Is there a part number we can use to purchase new caps instead of whole yagis?

There is no part number for the caps. We will feed this information back to our supplier and try to get to resolution on keeping them where they belong.

I just checked out some of our OEM Cambium yagi's and compared them to the KP yagis, and I have to say that it's much easier to pull the plastic plugs out of the KP antennas. Maybe this is happening to you because of intense cold and hot weather cycles year after year?

In any case, for both types of antennas going forward I'm going to be glueing the plugs in place.