Mine did this very easily when I bought it (used). Only way to get first reliably was to shift to second and then up to first. There was essentially no resistance to reverse.
One motor mount later, and there was no way you could make the mistake. Plenty of effort required to get over there to reverse. Night and day.
Posting this because if you do have this problem, you may well have another problem that is causing it--motor mount or shift linkage mucking up the allignment of the shifter cables perhaps.
Now I just have to remember not to throw my wife's five speed into sixth (aka reverse). That would be bad
