[AT&T Samsung Galaxy S 4 Q&A, Help & Troubleshootin] Camicia:
A mix of facts and speculations (I will try to make explicit the speculations - please call me out if I am wrong):

It is an hardware problem. I read enough post around to confirm that the largest amount of these problems cannot be fixed with software. For completeness, there was a bug with the 4.4.2 update and the sim cards that have a pin. The S4 was reporting no sim card. If I remember well it was fixed in 4.4.3 update. This is the only one solvable by software.

There are a lot of S4 models out there. Under the marketing name of S4 Samsung sells different models. The affected ones are the GSM models (T-Mobile SGH-M919 and the at&t SGH-I337 as well as the international i9505). The CDMA ones can have this problem but I read that the problem can be almost eliminated disabling the LTE... but now you do not have LTE :p

The Nexus 5 seems to have the same problems. [speculation] They share with the S4 the same circuit or chip that is generating this problem.

All cellphones have some devices that will have problem with the SIM cards. There are multiple reasons why this happen. Even in the same model (i.e. S4) there are different root causes that can create the problem. But once you rule out the SIM card and the SIM card reader, there is no luck. I am not sure what is the expected service life of a cell phone in these days but considering that a few carriers distribute the cost of the phone over 2 years, it should be at least 2 years.[speculation - I do not have the actual numbers] Considering the safe margins it is probably more around 3 years. In the case of the S4 there are more devices than expected having this problem. It almost seems that the failure rate is just above 1 year that is a lot lower than what was planned. If it is the case even substituting the motherboard may likely result with the reoccurrence of the problem in less than 1 year, so why bother to change the chip? BTW, which one? Candidates: U500, U501, and U203 :rolleyes:

They could not fix the problem through software. Samsung and their partners (i.e. carriers) share data on defects. From what you read around it and heard from T-mobile customer care, it sounds like this is a well-known hardware problem, and [speculation] they likely tried to fix it [See that_was_easy's post] with software but they were not successful.

They honor the warranty period of 1 year but they drop the ball on the rest.

All things consider, I wonder if there is a way to put enough pressure to Samsung to issue something like a "recall" out of warranty.

Maybe making the press aware of this and hoping that they will do something to show that they care about their customers.

Maybe something legal.... class actions are not the best way to bring good returns to consumers (just the attorneys usually come out happy) but Apple is facing one over the 2011 MacBook Pro GPU issues. I would even put my signature on committing not to participate in any future class action if they fix my device ;)

What do you guys think?

P.S.: The last attempt to fix this problem though software is this. In this the guys says that is running MDL Bootloader / NH7 baseband running Android 4.4.4. I will let you know how it goes.