I have a lot of experience with Canon Rebel series, so you may exclude the very basic solutions ;-) I have taken about 480,000 images with Canons 400D, 450D, 550D, 600D, 700D. I have a new 800D. 2 months old. I'm using it with fully charged original battery and another fully charged off-brand battery. I used it with 6 thoroughly tested 8GB-128GB full sized memory cards, among them Sandisk Ultra 80MB/s, 40MB/s, Adata and Goodram (very decent Polish brand). All of these are fast and allowed writing full HD clips without interruptions. I never had this problem with previous cameras. What problem? When the memory card becomes filled, there are moments, when the busy red light keeps on blinking and blinking long time after taking a photo. Normally it would take a second, suddenly it blinks for 1 or 2 minutes. When it keeps blinking, the shutter button takes a long time to respond, sometimes I click and it doesn't take the picture. Important: all the time, the viewfinder counter shows that the buffer is empty and ready and that I can take 9 RAW images. Well, I cannot. I can take a photo every 2 seconds instead of 4-5 photos a second. When I turn off the camera, the light stops blinking. When I turn it back on, sometimes it keeps on blinking, sometimes not. Mind you, no data is lost. I take a few photos and it blinks endlessly and slows down. I turn it off. I take out the card. All images are right there, nothing is lost, so I can't explain what it keeps on doing. After I change the card, it's OK for some time. One time, after card change, the camera wouldn't low level format a perfectly good card. I turned it off for a few minutes. Turned it on again. Now it formatted the card just fine. Important: I had some experience with really slow SD cards. It's nothing like that. With slow memory card, the viewfinder buffer counter decreases after each shot and it stops taking pictures when it reaches 0 (buffer full, now have to wait until image is saved to card). Then it gradually increases to 1, 2 etc... In my case the buffer is empty and I should be able to take at least 9 RAWs in quick succession, which I'm able to do unless the camera starts its blinking shenanigans. The issue occurs at unpredictable moments, but usually when memory card is at least half filled. Sometimes it's at 70GB point in 128GB Sandisk Ultra. Sometimes it's at 7GB point in 8GB card. Sometimes it's at 49GB of 64GB card. Only reasonably possible explanations I can provide are: Failing in-camera card writer Failing buffer memory What are your thoughts?