What you should do is the following;

1. Go to your Afterbirth+ folder in the My Games folder. On windows, this is "Documents/My Games/Binding of Isaac Afterbirth+/". On mac, this is "/Library/Application Support/Binding of Isaac Afterbirth+". (Thanks @DendroaS)
   
2. Locate "log.txt". If you find this, you're in the right spot. Locate the crash log from when it crashed. It's named corresponding to the date and time. (For example, "isaacv1.06.j85-20170527-174052-12596-5924.txt". Notice the 2017/05/27 at hour 17:40 and 52 milliseconds) Open it, and copy the entire file.
   
3. Go to www.pastebin.com, paste the *entire* log into a new paste.
   
4. Comment below your pastebin link with your log of a run that had an error occur.
   
5. Try uninstalling and reinstalling Godmode if it persists.
   It seems that some of my code may not be fully downloaded and it's causing an error because it can't find it.

To temporarily disable the mod from being marked as [Old], go to the folder "Documents/My Games/Binding of Isaac Afterbirth+ Mods/", find the folder for Godmode, and delete the file "update.it". If it marks as [Old] again, that means a bug happens, and you should immediately paste the log here.

Thank you, and enjoy Godmode! Updates will come periodically fixing the bugs I find and hopefully as many bugs posted below as possible, as well as adding more content.