Transferring Mevo camera videos from MacBook Pro

I have lots of large videos that were taken using a Mevo Camera and saved onto an SD Card. I am able to transfer the videos from the SD Card onto my MacBook Pro with no problem. Once completed, every video works through Quicktime on my MacBook Pro. However, I am running out of space in my cloud and need to transfer the videos onto a thumb drive (I am open to hearing alternative options). I purchased 1 TB thumb drives, which should offer plenty of space. Once I transfer the videos onto the thumb drive, I check to make sure they work before I delete the videos from my cloud. Some videos on the thumb drive work perfectly and others won't open at all, yet every video has the same formatting. When I open some videos on the thumb drive, a window pops up telling me the "the file isn't compatible with QuickTime Player". Not sure how that is possible?? Every video file is in the mp4 format. Also, using Disk Utility I have confirmed that the thumb drive has more than enough space left. I have had this issue on at least 5 thumb drives and I am probably using about 80GB of space on the 1 TB thumb drive. Any help would be greatly appreciated?