Bill, I would look carefully to make sure that there was not some other cause, just for CYA purposes. Around here, we get seasonal movement due to expansive soils. Of course, we don't have basements or bedrock and almost all of our houses are monolithic slab on grade. Wet and dry seasons can easily move a slab around an inch or more.

On the subject of Truss uplift, I was under the impression that both temperature and humidity could cause this phenomenon. Also, don't forget that the "lift" has to "settle", so a 6 month or so cycle might make sense.
Good luck.
Jim

__________________
Jim Luttrall
Mr. Inspector.net, Inc.
Allen, Texas 75002