PPP connection not working properly

RouterOS General
1

Hi Team,

We supplied 47 numbers of numbers of HEX router to one of our customer and
maintenance is also covered under our contract.
The router are used for two connectivity at branch, one is primary and as
secondary connectivity we are using 3G/4G USB dongles.
But some of dongles working fine and some of dongles are not working at all,
dongles are disconnecting frequently.
We are using below mentioned vendor dongles.

  1. HUAWEI MOBILE
  2. ZTE
2

Please reply if anyone having solution for above query.

3

There is a table of USB modem dongles compatible in the Wiki, also, will be good if you can specify the actual dongle model numbers