HxD breaking models?

I need some help with HxD Hex Editor. I had just got the program a couple of days ago and I am already having problems.
Whenever I try to change the cb_firestart string with an un-defined string named cb_idle_pistol, my model breaks.
I have no clue why it is the model keeps doing this. My only guess is that I’m doing it wrong.

Please help me with this ASAP and no rude comments =D

~ Cpt. Hazama

iirc it’s because there is 12 characters in cb_firestart as opposed to 14 in cb_idle_pistol. you gotta keep it the same length I believe.

edit: yes, watched your video. you’re overwriting non-sequence data (those periods) with your new text. you gotta keep that shit the same length.

Yes, I knew about that but I thought if you went to edit and insert bytes then you can add more characters?