Ultrasonic level transmitter

I have some questions related to ultrasonic and radar level transmitter.

There is a floating roof tank with 14 meter height, a FMR51 transmitter is installed on it.
Once in a two months ,there are lots of problem with them. Only information that I have for the problem is '' device hanging''. But I can explain you about history of solving the problem which has been done, without no effective conclusion
1- the engineering team changed the barrier, cables, cable distance to control room and Adding JB in path of cable, this was done only for easiest way of disconnecting and connecting the wires for restarting the device
2- removing streamwell of tanks which made the situation a little better.
I kindly appreciate if somebody could help me for giving a procedure to find a problem or giving some solutions for configuration, etc..