Thumbnail rotation problem

I'm noticing that a lot of my images after importing into LR have the thumbnail rotated incorrectly (and distorted aspect ratio). I think these are images that I rotated with another tool (like Photo Mechanic) prior to importing int LR, but I'm not positive since the folders are months old. The problem is that they are mis-rotated and LR doesn't fix it until I access them. So, for example, if I select a folder with this problem, and page forward in Library view... it will initially show the thumbnails wrong, then it slowly rotates them one at a time. Then if I page forward it will do the next batch. Is there a way I can get LR to fix the thumbnails all at one time so that I don't have this initial delay on every page of images I go to view. Once it fixes them, it seems to remember forever.