EOS R7 & RF100-500mm lose focus at 400-500mm

[lschaerer]

Hello.  I'm not sure if this is a camera or lens issue, but I'm guessing lens.  I've had my R7 and RF100-500 for 2 years.  About a week ago, I started experiencing a focus issue with the lens.  When zoomed to 400-500, it will be focused fine, then suddenly the whole scene blurs.  It will not refocus on anything until I zoom back out to 100mm.  The distance of the subject from the lens doesn't make a difference.  I'll be taking multiple shots of the same thing, focused clearly, then suddenly, everything is a blur.  It does work fine on MF, only happens in AF.    I've tried all the suggestions I can find on internet, checked all the switches, changed cards and battery, turned camera off and on, lightly cleaned contacts, but I haven't found a solution yet.  O

I've attached a photo from my LCD screen of the blur when it happens.  I had taken several clear shots in a row of this flower, then it suddenly blurred out.  I appreciate suggestions.  I know many are quick to say "user error" but, again, I've been using this combination for 2 years, and this is something that's just started happening last week. 

[lschaerer]

The repairman at my local camera shop did a factory reset which fixed the problem (the only thing I didn’t think to try). However, now I have to go put all my settings in again.  I’ll make sure to look at that.  Thank you.

[lschaerer]

Thanks.  I'm having to reset all my custom functions now, so I will check that.  

[ebiggs1]

"He said just like computers, sometimes things just get crazy in there, and when all else fails, do a factory reset."

I wholeheartedly urge folks do a camera reset when things go haywire but I will say it is 99.5% of the time because of a setting that the user did and not the camera going "crazy in there". It sounds like you have had a bit of a problem with your camera so if I were you I would send it to Canon and ask for a C&C just for piece of mind. If you are as you claim to be, it is imperative you have a working and dependable camera. The C&C will tell.