I don't know if it is still a limitation or not, but Windows historically can not produce an AVI over 2 GB in size when converting formats. I know that is the case through Windows XP - whether they have gotten around that or not in Win 7 or 8 or 10 I am not sure.
If that is still true, your only option is to try to pull a half hour and see if it works any better on the conversion. Your resulting AVI just needs to come in under 2GB.
That's my 2 cents!