Ethernet ports disappearing with RB2011 and RB493AH

Hi all

I have a strange issue on our sites. I was thinking I had a defective unit but now I think something strange is happening. Here the story

Just to let you know: I have extensive experience (something like 7 years with my infrastructure ) on mikrotik devices, the sites described below are cabled with outdoor cable (for example the ubiquiti tough cable and plugs).

One day I go to site1 and I think “hey it’s time to put a new router instead of this 5$ switch” so I put a new 2011 in the site. Everything looks fine and after a while I go back home. The day after the site is KO, like if the router has disappeared. I go there and I see that the router does not see any device on ethernet, I reboot it and it looks again ok. So I think “hum… let’s put a RB493AH” and that’s what I do…
After one day, the same story. So I go there and I switch the router with a RB750 (so it’s a plastic case) and everything is working, no ping lost on the ethernet. Now, I see that one radio disappeared but that’s paradise compared to what was before

Then I had to do the same operation on another site. I was reluctant to experiment again on the site, but I had to know. So I did the same, I upgraded the 5$ switch with a new RB493AH. After some hours the ethernet was loosing the packets, like 30% or more. I put a watchdog in the router and the devices to reboot and again the ethernet was disappearing like in site1. When I changed with a 750GL the site was working again as expected.

By the way, the sites are populated with old WRAP/ALIX cards so I was wondering if they disturb in some way at electrical level the routerboards.

Now the problem is that I am wondering if I am the only one having these issues or somebody can give me some hint.

Thank you in advance.

I have similar problem with RB943G, I lost packets at random times. Here is the post with my description

http://forum.mikrotik.com/t/rb493g-intermittent-packet-loss/58734/1