trail camera corrupt file

So I have had a huge problem this year with corrupt video files.  I am using crap wild game trail cameras and simmons .... but on public land, i expect some to get stolen so cheap crap it is...   That being said they worked fine the first couple years.  90% of my video files have been corrupt and won't play at all.  Nothing like having 100 vids on a newly scouted property that your looking forward to check out and then you can't see anything.  Its like getting a christmas present and being told you can't open it.

     Pictures seem to work, so I have switched most cameras to that mode.  I have tried the online recovery programs, but they don't work.  I reformatted the disks and kept track of the ones I thought were bad only to continue to find new bad ones.      Any ideas???   Anyone else had this problem??    I broke down and bought new sd cards to try. 

thanks for the replies .  I will be more diligent on reformatting. 

Like previous mention. Format card every time 

You need to format your cards on a computer, Once you do this it will wipe any old info or formats that may have saved on the cards. If you are running 2 different types of cameras do this and it will help with pictures and video