3g interface not coming up after replug

Hi !
I am currently using a cinterion's lte module connected to a qcom ipq4029 system.I am running openwrt with it with kernel version 3.14.43.
Sometimes my lte modules device node vanishes from /dev.The node are like ttyACM0-ttyACM4.
The ACM0 node is used for modem.When first boot the system everything works fine.But after some random time the node vanishes . We made a fix to bring up the node back by restarting the lte module as it's enable pin is connected the the processor.The nodes are back but the interface doesn't come up in the ifconfig .We have to perform either a network restart or network reload to bring the interface up so that we have a working internet
.So what is happening wrong here ? Is it hotplug scripts or netifd that not working as it's supposed to do. Majorly I need help to bring the interface back without performing a network reload or restart.Also I need to know what can be causing those nodes to just vanish after sometime.

There has never been a ipq40xx version of OpenWrt or LEDE with kernel 3.14, which means that you aren't using OpenWrt at all, but some heavily butchered up vendor (Q)SDK with its vendor kernel. While this SDK may be derived from an ancient OpenWrt version, all the relevant components have been replaced with vendor binaries. You'll have to contact your vendor for support.

Yeah. The sdk is from the manufacturer. But the openwrt being used in it is having netifd for managing the networks. Can you tell me from the openwrt perspective if we are missing something ?
Some directions that can somehow help us.?

Past @slh's likely spot-on assessment that "you aren't using OpenWrt at all, but some heavily butchered up vendor (Q)SDK with its vendor kernel."

Kernel version 3.14.43 tells me that the code your running is likely based on a reasonably old version of OpenWrt. There may be some hints in files in /etc/ as to the version that was used to derive your firmware.

With current OpenWrt, netifd often runs scripts in /lib/netifd/ on the device. Current source code for OpenWrt is available at https://git.openwrt.org/openwrt/openwrt.git

Much past that, you're likely at the whim of whatever your OEM/ODM did, and is willing to support.