How does it 'lose' the connection?
What are the timespans involved.. minutes, hours, days?
What network/bands are you on?
How far from the mobile tower?
Whats your signal strength?
Does your antenna have free line of sight or are there obstacles in the way? What? Where? (look up 'fresnel zone' to get an idea what is involved)
Is the RUT950 moving or stationary?
What antenna do you got?
Have you tried the 'keep alive' option in the mobile network settings?
How old is the RUT950? What firmware have you been running before downgrading?