I’ve had the RUTX50 for two full years - very happy.
I’ve been streaming live cams to YouTube for two years non-stop via the RUTX50.
I make 20-25 TB of data traffic per month through this device over the LTE/4G network.
I invested in expensive directional Iskra P-60 antennas with a strong gain of 11 dBi (4 antennas). The base station is 3 km away. Due to the excellent signal, I also have excellent LTE/4G speeds.
The problems with the speeds you write about are mostly because the antennas that come with the device are weak and omnidirectional.
When buying new and external antennas, people often do not pay attention to antenna gain and directionality (and which bands they support).
Sometimes it is necessary to use cell lock to get more aggregations or connect to a specific base station that is not congested.
The modem simply works poorly when it has a weak signal, I’ve experienced that myself. Buying strong and directional antennas solved everything.
It is important to connect the antennas in the correct order due to polarization (example for my antennas)
If only two antennas are used (2x2 MIMO), the same connection order applies, numbers 1 and 2. Other combinations will not work (I personally tried all possible combinations with only two antennas/cables).