So today I tried Halo Map Tools for the first time. I decided to mod the level Pillar of Autumn, or a10. I swapped the meta codes for cyborg and marine_armoured. I also did this for a30, or Halo. I started up the level a10 and noticed the animation of Chief stepping out of the cryo-tube was messed up. There was no Master Chief, but I understood why as soon as the camera tilted and showed the marine standing right next to the tube. This was no big deal, but then I wanted to revert the level to normal and I had indeed made backups of all the levels. I tried replacing the modded a10 with the previous untouched a10. I opened up HMT to see if the damage had been erased. To my surprise the meta codes were still swapped on both levels. This was frustrating as I did not know or could in any way possibly remember the meta codes. I did not think to write them down because it didn't seem necessary at the time. All modded maps wont be replaced and HMT it seems automatically re-mods the levels if I try a reinstall, even if I check the "restore corrupt files" button on the reinstall options. I really could use some help with this weird experience and I would appreciate any help given to solve the situation as I would still like to use HMT in the future.

Maybe something is happening with "compatibility files" and your new maps are put in that folder. Do a quick search on that. Also, if all else fails, just reinstall your Halo, and everything will go back to normal. This is also a Halo Custom Edition forum, rather than a regular Halo PC modding forum. Custom Edition allows you to play custom maps made from scratch, rather than playing modded default maps.