That is what I think of it - this assumption.may not meet reality
Meanwhile I am using the latest FP OS 1.8.1 and have two sim cards plus a 128GB sd card right from the start after I have received my phone in February. Also using every available sim network setting and also GPS + Wifi never caused a single problem no matter which FP OS version was installed.
The phone works reliable for me since quite some time now, but I keep it non-rooted.
I tend to promise you, it is not the phone.
You seriously got three?
I cannot think of any other manufacturer doing something generous like this when a customer reports troubles with a product.
But still it did not help.
I think by now it is time to try something different at this point.
To me it rather looks like a bad app combination causing negative interference or just a single app with faults or maybe compatibility troubles. Such things may happen although it is stated the app would work with whatever OS version. You can read this in many reviews. For some users it may work, others have troubles.
Not sure if your phone is rooted because of "aLogcat ROOT", but if so try to use it non-rooted for some time and get your apps installed approximately step by step and not all in a row and give the phone some time of using to see if it operates reliable.
Going through the same procedure over and over again switching phones does not bear the chance to get this issue fixed. Try to use the "elimination" method, also operate the phone without sim card for some hours. Just try different approaches as you do not know for sure what´s the cause.
If you honestly believe it is a general phone issue, how about telling the support exactly what you are doing. They may be glad to pick out a random phone and do the same to maybe track down a never before revealed problem.
I hope I could deliver an idea that brings you closer to the solution. Good luck anyway.