I have switched to another ISP because after 2 years of smooth sailing, we started to have upload speed issues and they didn't care. Strangely, the new ISP has the same problem: from time to time, upload speed goes away. When this happens, Speedtest measures 4 ms ping, 8 Mbps down speed and 0.01-0.02 Mbps up speed (or the upload test hangs).
This slowdown happens seemingly randomly, several times a day, takes 5 minutes to an hour, then goes away. ISP says they are seeing big packet loss, but they have no idea why.
I'm about 1300 meters away from the base station and when installed, measurements have shown -70 dB signal strength and sustained speeds of 20 Mbps up, 50 Mbps down. (I didn't check signal-to-noise ratio and now I don't have the password for the AP.)
The AP (Ubiquiti PowerBeam PBE-M2-400) points about 10-15 degrees away from optimal direction because the installer didn't have the right console. The old ISPs antenna (a different Ubiquiti model) pointed the same bad direction for 2 years without a problem. Both ISPs have their base stations on the same water tower.
I'm starting to suspect that my problem may depend on other users' usage pattern (of the Internet or their microwave, don't know). Not necessarily from even the same ISP.
Can this be caused by the wrong antenna direction or the problem is elsewhere?