If it comes up again in a few hours then maybe you have some damage on the way. Oil lubricated bearings can really generate some strange data if their not lubricated adequately. This example is at the end of paper. Somehow this link didn't make it on the first try. A trick we use to see when the bearings needs greasing is to monitor the 4KHz to 8KHz band.
Poor lube seems to show up very well here.
Watch this parameter and when you see it trending up take out your grease gun and give it a few shots. Check the trend again and you will see it drop to the normall level. If it comes up again in a few hours then maybe you have some damage on the way. Oil lubricated bearings can really generate some strange data if their not lubricated adequately. This example is at the end of paper.