I have good news so far. I've taken loads of pictures, and videos in both full hd and the UHD size videos and both are good with this new card. I don't know if it matters but this new card says it writes up to 40 mb/s 266x, where as the PNY 64gb 10 class I had only wrote 10mb/s. But it was probably just the card altogether. I also talked to another person who was having the same issue and they told me that they also had had one grayed out pic on their devise, not on sd card BUT that he said he believed that it happened when he was trying to move pics from SD back to devise to try and save them when they had been corrupted on a bad card, but that only one went through because of the bad card. So that was very good to hear also for me since I couldn't understand one being on my devise, but I did indeed try just what he did.
I have even saved a couple tubemate large videos off youtube to card and SO far everything is great. This card is noticeably faster than my previous card, so right now I'm a very happy camper! I was also so worried about having to exchange yet another phone since the first one had a bad power button. So right now I'm really loving the phone, knock on wood, haa.
Now I'm just going to have to take another chance and order this same card on Best Buys website in a 64gb at least size since no one around here has them in stock. I'm taking so many videos (between my dogs and my new first grandchild) that I know I'll fill this 32gb up fast. I'm really surprized that your Samsung was bad because most of what I read when people have a card issue it's with a Sandisk and they all say to only get a Samsung, but this Ultra Plus seems really good, so I'm going to try it in a larger size.
So anyway, I think it's your card as well and let me know when you get a new card if that fixes it and I hope to keep happy with this one.