Raymarine instruments had a big dream last night

[BelleSerene]

Our Raymarine log has been playing up. Sometimes when we turn the instruments on, the mileage hasn't been the same as when we last turned them off. One night last Autumn, we apparently did a good 10,000 nm. Which doesn't greatly bother me, except that if this jittery memory were to happen while I was at sea I'd lose the ability to plot an EP.

We use ST6001 instruments with a C80 chartplotter.

Does anyone have any idea why this might happen?

 

[nigelmercier]

Does the reading revert to normal, or is it accumulating?

 

[BelleSerene]

Does the reading revert to normal, or is it accumulating?

It's accumulating now from about 17,200nm. There have been a few such new starting points. One was even less than the previous closing value.