Even I'm using the device with a jio and Airtel Sim, I use Airtel as my main sim though and so far I have never experienced any issues, faced issues with jio but internet connectivity for jio is actually poor in my region so can't blame the device for the same.
But you are not alone, there are many people in this forum who have complained about network connectivity in M30s, and so far nobody's problem has been resolved via update or any means.
In short, I do feel that it must be a device specific issue. But the service centre people will simply tell you that it will be resolved in a future update. So, there's nothing that you can do as of now to fix it, just hope for the best.