This thread is not for help but for information about this error. Googled 30 minutes for it without any solution and had to try everything in zmodeler... Finaly found a fix.
The _hi yft was 10mb, and the non hi 14mb. When spawning via trainer, the game crashed and throw a err_str_failure_3 error.
I had 4 LODS of rims (just a copy of the lod0, about 50K poly). I removed the others lods of it. The files was reduced both to 10mb and it spawned without crash.
So, if you get this error, try to remove lods and try again.