Intermittent Temperature Transmitter Signal


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We have Rosemount 644 temp. transmitter taking from RTD to Siemens DCS through SPD. Intermittently, the O/P signal from transmitter going to LRV for very short time of nearly 90 m Second and return normal by itself. this happened randomly yesterday and also from 3 weeks without any clear reason. Can Temp Transmitter failed by this way? Any suggestions why this happen?
From the 344 manual:

"If diagnostics detect an input sensor failure or a failure in the transmitter electronics, the transmitter drives its output to low or high depending on the position of the failure mode switch. If the sensor temperature is outside the range limits, the transmitter saturates its output to 3.9 mA for standard configuration on the low end."

3.9mA is lower than the LRV at 4.0mA but it could be overlooked.

So, yes, the transmitter can go drive low in failure mode.

Disconnected sensor wires or shorted wires can also produce a failure mode action.