Anyone know the secret to get a sagemcom router?

If you think an Arcadyan or Sagemcon gateway is going to resolve issues and be internet nirvana well the obscurity and a lax support engineer might be a path to take but it might not resolve the actual root cause of the issues and might make it more difficult to trouble shoot and know what is going on. Before jumping into that bag of snakes it is good to know a bit more. The three gateways are each from a different hardware vendor but the reality is that the two newer gateways are not all that much of an improvement if any over the original Nokia. You might be trading one problem for otros. The policy is to replace like with like, but why does T-Mobile seem to say one is not better than the other they are intended to be “equivalent” gateways. The Sagemcon was added to the hardware pool to provide more inventory for new deployments with new subscribers. There is an article about this, seriously.

So, beware what you wish for. I have had a Nokia gateway since the middle of January 2021 and I would not trade it for either of the two newer ones. All of the issues we have experienced here have been with T-Mobile's cellular equipment upstream. The Nokia I have has never had any heat related issue, no SIM card carrier issues, no power problems, and no major flaws. Maybe it has some warts but I can overlook those. Each and every time we had 5-6 days of disruptions it was always due to some upstream problem. Every time. I don't discount the possibility that the gateway you have could have an issue but you might not improve the solution with a gateway swap. You might just be introducing new variables and not like the more limited management of the gateway with ONLY the mobile application. The Nokia may not be a great gift to mankind but it does have more configuration capability, and a WEB GUI management interface that is useful. The cellular metrics are easily accessed via a browser OR if you want the mobile application. Not so with the other two gateway offerings. I find the mobile application a bit fickle and often I have seen it crash or hang up my phone. Maybe it has improved but it is not obvious to me as it still is an argument every time I try to use it. I am grateful for the WEB GUI management option. 

It is possible the location you are in just does not receive sufficient signal strength or quality. It could just as well be there are problems with the cellular equipment your gateway connects to. It might be possible that they could force the gateway to another tower. If there are other towers I have seen them use this as an option and in some cases it was successful. It really is good to know where the problem really is. No I do NOT work for T-Mobile and have no incentive to mis-direct you.