Hi Dear,
As per your query which shows that there is no issue with router level, however i would like to suggest you that, there are number of problems that can lead like this kind of problem occurred.
1. Need to thoroughly check A/C & DC power system. High / low voltage can be disturb equipment behavior.
2. Check connection of power adapter to the AC power plug.
3. Installation of device should as per Huawei standard.
4. Maintain environment of equipment room, i mean to say, help to control the environment temperature. subsequently resist to replace the hardware which becomes faulty due to weak environmental conditions.
5. If the environmental conditions are OK, there might be issue with air flow, requirement of filter cleaning, etc. Mostly door of system room remain open due to this outside dust get enter inside in equipment.
So need to address these issues at level.