.........Also it is consider in very poor taste to "Watermark" your imagery... Typically done by amateurs who don't have a clue about professional protocols...
Hogwash! I know several professional photographers that mark their images when sharing anywhere on the internet. They all are certainly not acting in poor taste are they?
I have been there but was focused on motorcycle racing at the time. Pretty sure there were a few sunrises and as many sunsets but I never noticed them.
Ebay is notorious for counterfeit SD cards. It is possible you got a hold of knock-offs. If that is the case some devices are going to have problems with them. Buy your SD cards from Best Buy or another reputable seller. Ebay is great for some things. SD cards are not one of those things.
I have been using one on my 80D for a couple of weeks. I like it and for me it is generally sharp enough. Zooming is smooth and hitch free. The lens appears to be well built and nothing rattles or moves around. It is not super heavy and is fairly easy to carry around on casual day trips and light hiking. I am a hobbyist with my main target being primarily astrophotography and then outdoor/nature type stuff. I have other lenses for nighttime sky images. I have noticed the Tamron 18-400mm likes good light. But who doesn't?