How can I tinker with the coding for cards in 1.6.13?

[Fregnor]

In previous versions of the game, when I have found an issue with a card, I have reported the issue so that the programmers can fix it in a future version, and then sometimes I have been able to go into the coding and make a temporary fix for my own game right now. This has mostly been to do with which token image or selection of token images I want displayed in my game. But in 1.6.13, if I make one tiny change to the coding of a single card, it prevents Forge from loading up. The bar gets to 96% and then freezes. Then I have to reinstall part of the game before it will work again.

How can I edit the contents of cardsfolder.zip without breaking my game?

[Fregnor]

It seems that the situation is not what I thought. I can still edit the coding for cards in ways that I have in the past, without breaking the game, and I can edit it in some new ways too:

-I can change which token image a card that summons tokens uses for them.
-I changed a card with First Strike so that it had Reach instead.
-I changed this card so that the text said that it had Reach instead of saying it had First Strike.
-I changed its Power and Toughness.
-I changed the wording of the sentence describing its effect.

None of this broke the game by making it freeze at 96% loaded.

But each time I tried to to add the Reach effect to a card that did not have it (but should have had it) it would break the game, and ruin that file, so that even if I removed the change so that the coding was just like it started out as, the file would still be broken, the whole game would not load, and that little piece of the game would have to be reinstalled to fix the problem.

I have a couple of theories:

(1) A single syntax error in a single card file will break the entire game and keep it from loading.
(2) There is something dependent that I do not know about. Like an external file must be changed in addition to this file if I change the number of abilities of the card in this file. Or maybe there is some other piece of code in this file that governs how many abilities this card may have that must be changed.

Anyone have any ideas what is going on?