I Have a problem with my MikroTik LHG LTE6 kit (RBLHGR&R11e-LTE6). After 2-3 hours the download speed drops from 60-70mb to equal 10mb,
the upload speed don`t change is always 18-20mb. When i reboot router the download speed back to 60-70mb.
hecatae is right.
You should check the carrier aggregation data for the link before and after the speed drop.
This will tell you if you need to enforce Cell Lock.
However, if the drop is due to poor signal, then Cell Lock might result in LOS from time to time.
Play with the settings and see what works best. YMMV.