This is a problem for quite some time. I think i wrote something about this on the old forum so it must be a problem throughout at least CEV.

Problem:
while generating cubemaps with one or more environment probes the engine keeps culling vegetation objects resulting in incorrect image based lighting of the level.

easy to replicate:
1. create a dense forest with the vegetation editor and place a local environment probe in the middle 2. Create a cubemap and check the result in a chrome sphere. As you can see in the reflection most of the vegetation behind the camera has not been picked up by the environment probe.

The solution I've found to this, is to go to the position of the probe, fly 200-300 meters up in the air. Then look down towards the probe and generate the cubemap. Then the vegetation objects will not get culled away in the cubemap.

Hey fancysweetroll, thanks for your reply.
Yes, this little trick works indeed but it only works for this one specific local area you want to prevent culling from occurring.
Sadly it also doesn't work if you pan out until you have the hole map in perspective.
I don't think this can mend to be the way Crytek wants it to function. Or can it?
It's broken for at least more than a year by now. I wonder if this bug is persistent in the main branch. All what it needs is to fix it is to automatically disable culling when generating cubemaps.
Would be nice to see some sort of recognition by the Crytek staff. So we know at least that this problem has been recognised.*hint, hint*

Good news. I just checked in preview 3 of 5.5 and this problem has been finally fixed! Hopefully it stays this way from now on.