Lens comm error with brand new Tokina 16-28 f/2.8 at-x pro

I could use some help.
I just purchased the lens from a not so local shop (2.5hr drive) I actually mounted the lens to my 5diii in store before I purchased. took several shots at multiple apertures. I was satisfied enough to bring it home with me. Here is where my issue starts. I am not getting Faulty comm error with the lens on my 5diii and 6d. I tried cleaning the contacts but that did not seem to help much. I have not had much of an issue with this before except for the occasional error, turn off, turn back on and continue shooting is how I've always fixed the issue.

I think I stumbled on the fact that it may be a particular aperture that is causing the error. So I began doing some more scientific testing and here is what I have come up with.
I can successfully take a photo at f/2.8, 3.2, 3.5, and I get an error at f4.
I power cycle the camera and start over- success at f/2.8, 3.2, 3.5, SKIP F/4, 4.5, 5.0............f/22 back down to f4=error

anyone got any ideas for me.

I've taken hundreds, if not a thousand or more pics with this lens and 6D and only had one problem when I was out in the freezing cold and wind one night. It cleared up with a power cycle.

That's quite a drive, but I would be looking at a replacement, not a fix. Maybe the shop could set you up with free shipping?

Is it happening with half press or shutter release? Pretty sure mine was with half press/AF.

With shutter release. Half press obtains focus confirmation like normal

I went to buy this lens as a cheaper alternative to the Canon 16-35mm 2.8. I got to the store, tried it on a 6D (the attendant wouldn't let me try it on mine) and had a lens/body communication error.

I never went further than that and left the store disappointed as I had geared myself up to buy it. I used the Tokina 11-16mm on my 7D for 3-4 years with absolutely no problems though.

That's good info to have Lewisc. I was wanting to use this one as a less expensive alternative to the 16-35 f/4 as I was attempting to save the extra $ toward a much needed 24-70 2.8ii. I may try another one, but I'm extremely leery since its such a drive