x6m altimeter problem

[avvtre]

Please, excuse me for my bad english!
I write from Italy.
Last May, I buyed a Suunto x6m.
I used it as an altimeter during my july's vacations on the Alps.
Sometimes, not every time, standing in the same place, the watch shows really different altitudes during approximately a minute or so.
Example.
My altitude is 2300 mt.
In a few seconds the x6m altimeter shows a sequence as: 3200 mt - 1900 mt. - 2900 mt- 3300 mt. - 1500 mt.... Only after a minute or so, he stops on the (correct) altitude.
It seems like the altimeter was totally "lost", and that only after a seek he found the correct altidude.
Is this normal?
Note that everyday, at the start of my excursions i setup the watch to a reference altidude taken from a map.
Can anyone help me to solve this problem?

	Suunto Visit SuuntoWatches.com to see Suunto's full line of wrist top computers and compasses.

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[roadcoach]

I have noticed similar behavior when I have used the watch when flying in a pressurized cabin. After switching the watch to the altimeter mode it takes a few seconds for the watch to update the altitude. I suspect that the watch does not keep continuous altitude records unless you are recording altitude or have the mode set to altitude. Perhaps this is a way of saving power.

[avvtre]

My problem occurred when i'm walking in mountains, the watch is in the hiking mode by from the start of the trail and after a correct altitude setup in a known place.