Hi Jason, I wonder if this is/was just a temporary problem with Instagram's CDN - as I was compiling information for a support ticket, looking at newer posts as examples, all of the new URLs I tried worked now. The URLs I provided above were from an older dataset we collected a few months ago. Although these three still don't work, some others from that dataset that didn't work yesterday are working today.
I think we can consider this a temporary issue. Thanks.