My 5R randomly showed f.-- in different modes. There is no way to control the aperture value of the 18 55 kit lens. Occasionally, the focus points are not shown normally. It apppeared to be a huge green rectangle surrounding the whole LCD screen. Camera not set to zoom. Focusing is working fine.
I have searched several forums and was given to understand that there are various causes to this problem.
a. contact problem (cleaning is required)
b. broken aperture mechanism (send camera to Sony for repair)
c. broken flex cable as part of b above (same as above)
d. loose mount ring of the camera causing a above (contact problem)
e. unidentified problem and can't fix by user(send to Sony for repair)
I have finally find a way to fix it. (not sure if it is a permament fix. at least it doesn't show the problem any more after my little diy repair)
Before I share my diy repair, I want to invite your idea and experience.