"Bad" content for DL2 / DL3 / Axon

I attempted to load some custom content into my DL2s yesterday and had a problem with one of the files. I could see it as a thumbnail image in the CMA, but the DL2 created a duplicate file with the name filename.jpg.bad. Tech support told me that this is what happens when you upload an incompatible file. I checked the Custom Content FAQ and all the parameters of this file seemed to be in line with what is listed there. Does anyone have any insights into what can cause a file to be rejected in this manner if all the listed parameters are correct? Inquiring minds want to know....