[Galaxy S 4 Q&A, Help & Troubleshooting] deleater:
Hey there!

I need some help... I'll try to describe correctly:

-First of all, I use i9505.

-After flashing this ROM based on Lollipop 5.0.x I've faced a lot of troubles which are somehow connected to work of the modem, as I understand it.

Previously I was using original CM based on Kitkat. I've also tried to flash 2 other Lollipop CM roms, nothing ever changed.

-Occured problems have several symptomps, which are:

1) while having incoming/outcoming call, the signal indicator would be "empty", as if there was no signal at all;

2) signal is quite unstable comparing to what I can call a normal work, the indicated level of the signal jumps often, such thing never occured when I was using Kitkat;

3) the modem would freeze after some actions which I couldn't specify, so I have to turn the airplane mode on to reboot it;

4) if the N 3) sympton occures when battery charge level is below 30%, airplane mode won't help: the signal indicator would show some unchanged picture (i.e. it shows 3 bars level, after turning the airplane mode on it shows none, but the name of the provider still shown (which is not normal), then after turning airplane mode off the same 3 bars will be shown, still I can't make a call, nor receive it along with other things like sms, internet connection etc.).

If I reboot the system at that point, the phone goes into bootloop (Samsung logo - ROM logo - reboot). One of the easiest ways to resurrect the phone in this situation is to plug in the charger, in this state it reboots successfully and the resources initialisation process begins (as if /cache and /dalvik were cleared). It all looks like if there was no power for the phone to boot... but despite this feeling and some energy used above normal, after booting the indicator would show there is some (i.e., bootloop occured at 30% point. After booting the phone, indicator shows 15-20% or something close to this).

Some time ago the situation got worse, now the bootloop occurs at 40% charge lvl, while running online games with mobile data working (didn't notice if it happens while connected to wi-fi) random reboot happens.

To solve the situation I've tried this:

-When I faced that problem for the first time (not long after flashing the ROM), I've tried to find some info. What I found was the post from CM comunity that there was a problem with modem drivers which had no solution by that time, and it was only a suggestion.

-Now, after some time passed, I've got fed up with this ... nice situation, and decided to find out if there is a solution released wich may be no implemented into CM updates.

I've flashed the latest MODEM / WIFI-FIX and BOOTLOADER GT-I9505 presented in the linked thread;

also flashed the latest ROM version to check if there was a fix implemented;

and flashed alucard's kernel (which seems to feed on the battery kinda like a big mutant-vampire! :-\ )

None worked so far. Still have all the problems mentioned above.

Any suggestion or, may be, known solution?

UPD solved the modem bug, it's stable now. But reboots @ charge lvl below 25% happen if any action is made (run a program; make/receive a call, etc.). Bootloop follows after such reboot, if the system didn't boot on the first attempt. To boot successfuly it still requires to be set on recharge.

Sorry for mistakes, hope my lvl of english is enough to let you understand ideas described above, thank you :)