Hi everyone.... -same Samsung S5 Gallery problem here. Problem first started right after putting a new SD card (class 10) into the phone and saving pictures into it. Gallery would take forever to open… lost cause. So I figured the new memory card is DOA even though it looked OK after running diags via a PC. I got a new one anyway, Samsung brand. No more problems so I concluded the first card was just bad. After putting about ~2500 pics on the card, the problem started again. Plus my Google Music (which saves to the SD card) is also freezing.
Clearing cache of data on the Gallery app sometimes will fix the problem but the problem is back in a minute.
As for Google music, the problem is really inconsistent so it’s hard to figure out what’s causing it. It may be OK for hours and all of a sudden the music starts getting choppy for few seconds or couple minutes.
I suspect it might be some app interfering with the card. I moved few apps to it so will start taking them out by one to see if the problem goes away. Not much luck removing Verizon’s bloatware because it always finds a way to come back. It may also be some AV issue (from AVG or Verizon) that’s scanning the card, not sure but I may try to disable it. I did tried finding some diag apps for the card but there’s really nothing good out there.
It can’t be the phone because I replaced the phone between the first and second card due to unrelated issue (faulty headset jack, sounds would play only to one earbud).
I found Samsung’s Kies backup software to be a waste of time too. All apps and contacts come back from Google account anyway, and pics are on the SD card, so what’s the point.
Anyway, I’ll get back to all if I find something. Maybe this tread can help someone else

I can’t find anything similar out there. Switching to QuickPic for now.
K
P.S. In regard to the phone insurance, check out the article from PC Magazine -The Great American Phone Insurance Rip-Off (just google it, I can't post a link here).