I'm not using a flash. I did what you suggested; put the shutter speed at 1 second and took a picture while looking inside. The mirror seemed to move smoothly. Started at a one point and when I clicked slowly moved up and back to the starting point. Did this also at 1/500 and same results, of course just faster.
I'm not sure if this might be related to my current issue, but prior to this major issue I noticed the camera was having difficulty focusing in the daylight. Once it got darker the pictures went back to being sharp and in focus. But in the day it was a hit or miss. I used different lenses, to see if the issue was the base or the lens. Same issue with both lenses.
Did not mean to divert from my current issue, but was thinking maybe the two might be related. Just throwing that out there as I am a amateur/newbie with cameras. Thanks to everyone so far in helping....