EOS 5D Mark IV Battery Grip Causing Memory Card Issues

[km24]

Hello

I recently purchased a refurbished BG-E20 battery grip for my Canon 5D Mark IV. I have had the Mark IV for a few months now and have had absolutely no issues with the memory cards or images or the camera itself. I recently shot a wedding and used the battery grip, turning It on so I could access the grip control features. When I did this I was seeing the preview of my images at first but when I went back to view them on the camera It said preview cannot be displayed. I captured them on all on CF card thankfully but the SD ones were showing issues. When I did not turn on the battery grip controls I did not have this issue. Both the SD and CF cards were formatted to the camera. I was shooting with SanDisk Extreme Pro cards. I'm imagining the grip is the issue but I am a little confused as to why. Has anyone else experienced this issue?

Thank You 

[Waddizzle]

Welcome to the Canon Community.  Sorry to hear you are having issues with your gear.

I agree.  The refurbished grip seems to be the culprit.  Have you tried removing it?

Where did you buy it?  I am not aware of Canon USA selling refurbished battery grips.  Was the item advertised as “renewed” or “refurbished”?

[km24]

Hello

Thank you for the quick reply. It seems if I leave the grip turned off the issue does not exist. It is only when the grip is turned on. 
The images on my second card, a CF we’re not corrupted. 
I should have clarified better. I bought It on KEH It was not refurbished. 
Thank You

[normadel]

It sounds like the grip is defective. Return it to KEH.

Even the good used equipment dealers are not perfect in finding something wrong with their wares. They may say "Fully tested", but you don't know how fully that is. That's why their warranties are so valuable.

[km24]

Thank you everyone! I am going to try to return It. I appreciate the validation in my train of thought before attempting to return.