Just check that you have 4g coverage on the frequencies supported by the SXT LTE. 800 MHz is not supported, and this is the 4g band with best coverage in rural areas.

I use a Huawei B593 connected to a RB750 used as a openvpn endpoint. It has been running since June, when it was installed, without need to reboot.

I have a Cisco WIP320 phone. It is not the same phone as yours, but I my experience is that it is nearly useless. I have only got it to work with WPA and TKIP, not WPA2 and AES.

Check if your laptops have 5 Ghz wifi.

6.3 is older than 6.24

I had to kill the Chrome task to log in after upgrade. Then it worked again.