Thank you all,
We found the problem.
The preamplifier from the 240W TOA. It was hard to find because the distortion showed up randomly, but it happened that just when we tested one TOA with one mic and no other devices or connections, it sounded VERY distorted. We copied the settings to the other TOA and moved the same mic with the same sound source and everything was perfect. We moved back to the first and it was extremely distorted.
The temporary solution (until we send the TOA to the service) we came up with is to put the unimportant mics on the defective TOA and connect the output to an auxiliary from the low power TOA, then processors, split, volume controllers and back in the two power amplifiers of the TOAs.
If the distortion doesn't affect the overall sound quality we will leave them as they are. In case it appears we hope that only the unimportant mics will sound distorted (again, it's not a continuous buzz, it sounds like clipping, so it shouldn't be noticeable when not talking into the mics). If, however the distortion affects the sound quality, we will just close the auxiliary and loose some mics. Either way we have sound both indoor and exterior.
I don't understand how, but without touching the gains (everything set to 0) all the volume meters show almost the same values, no clipping seams to occur, everything seams to work very good including the sound quality (so, after trying to understand all that db/dbv/dbu/dbm language, it seams that the default settings are all that was needed). We are just waiting for the distortion to reappear to see which of the two approaches we choose.
Inour first setup the defective TOA sent the signal to the processors, thus we entered the chain with a distorted signal.
And as a side note, we found out that it may have fallen from where it was (the rack is about 2 meters in the air
If something else comes up I'll post here, otherwise I guess this post is complete and thank you