[Q] [i9506 with Temasek's UNOFFICIAL CyanogenMod 12.1] MMS not working properly

Hi,

I've been using Temasek's UNOFFICIAL CyanogenMod 12.1 on my GS4 Advance (i9506) since quite a few months (i.e i've used 3 different versions, until current version), and with none of them my MMS's have been working properly.

What happens : I can't send or receive MMS with LTE alone. Sending always fails, and I cannot download the ones I'm receiving.
My phone does something weird : when it tries to send an MMS, I can see the data connection being lost (I have the exclamation mark beneath the network bars).
After the send attempt fails, I have to manually turn off then back on the data connection to actually get it back.

What's even more strange is that my MMS work fine at home when I'm connected to my home's internet through WiFi o.O

LTE alone = big nono. LTE + WiFi = OK.

In the rom's developpement thread, I've seen several people complain about MMS not working for 'em either but there are also others saying they just work fine for 'em, so... Seems to be a quite unusual issue.

I've tried a data and cache wipe, even a fresh install, the problem remains.

I'm starting to think about going back to Samsung's stock rom for this reason but that would really be a shame... :(

Anyone having the same issues...?

Thanks in advance for any kind of answer :)

Have a nice day all.