Yeah, I wanted some hardware details about the modems, mostly manufacturers etc.
The PPP fix works for me on 3G and PPPoE. Which I think covers it. I can reliably lockup the 3G connection on a ZTE modem though, I blame the ZTE modem for that mainly. Not having any issues with Huawei modems, they stay online for weeks. My 3G signal here is so-so. So every now and again it drops, the huawei just drops out of data modem with no-carrier and on it goes.
The ZTE device does not, which means we can't talk AT to it unless we reset the device, which can only be done over the application port which is just wrong.