I have some videos that I have downloaded from YouTube (mp4a) and when I try to save it in my 2nd Gen iexpand 64 gb it returns an error saying that it failed to save some files.
Is there a limitation regarding the file format or file extension?
No limitation that I am aware of. Unless someone formatted the drive at some point to be FAT32. FAT32 has a file size limitation of 4GB which could cause the problem your seeing. There is also the possibility of damage due to unsafe removal of the drive at some point. Running a chkdsk command on it should resolve that though. But without knowing what OS you’re running and what you’re using to write the videos to the drive and what the error message shows exactly it’s hard to know what the problem could be.