Eas problem. Any hints please as to cause ?

Year 2001 P38 R/Rover diesel Auto. Garaged outside and used reasonably infrequently.
Last Friday left home at about 7pm. Temperature outside was about - 5 degrees although it had been nearly -10 overnight. Suspension was quite slow in coming up. About 5 miles from home after travelling a few minutes at over 50 mph the lower light on the EAS switch started flashing that it was lowering the suspension. It tried for some time to lower (light still flashing) but eventually failed and the 35 mph sign came up with all 4 lights lit up.
Checked the fault codes today and apart from "7 vehicle has moved" there was a code "2 RL valve stuck closed". Cleared the fault . Started engine and the car almost immediately came up to correct level - so presumably the reservoir was fairly full ?
Everything now seems to be behaving normally.
Can anyone tell me please : -
1. Is this an indication of future problems looming ? (I rebuilt the valve block about 4000 miles ago) If so any idea of the likely cause ?
2. Could the valve block have been affected by the very cold weather causing the valve to stick closed ? If so, is there any way of avoiding this in the future ?
3. any other ideas or theories gratefully received.

Or is it just "one of those things" that you have to put up with if you want to preserve the EAS system on a P38 ?

Many thanks for any ideas/suggestions

Check the connector on the Rear Left height sensor for corrosion as a first step. Could be the first sign of the sensor failing.

R/L valve stuck closed does not actually mean the valve is stuck. It could just mean that when the valve was open no change that the ECU would expect to see took place on that corner. As Keith says more than likely a faulty sensor.

Wammers and Datatek very many thanks for both of your replies. I had a horrible feeling that it might be an indication of something else in the future. Will check the connector and sensor and hope for the best. Many thanks.