Customer service reps have ZERO control over firmware.
Modem manufacturers create the firmware for devices they make, then make the update available to the ISPs. ISPs then send the update to devices on their respective networks only when they have fully tested the update and certified that:
1) It is important,
2) It is necessary,
3) It does not adversely impact the network or fellow customers.
Having said that, your problems are likely not caused by firmware but are rather classic signs of a signal problem caused by damaged coax or loose connections. Post the modem's signal levels page from 192.168.0.1. Something obvious may jump out.