Yeah, that kind of typo will throw off any translation software 
It doesn’t even parse 人がいぱいいる - just gives no results for ぱ and る and assumes it’s 人外◯いい◯ essentially. When I change that to 人がいばいいる it does give me the result you were describing. I can see how that’s confusing
Strange results like that are a pretty good sign you’ve got a typo somewhere. Ichi is pretty good at parsing sentences, and especially a manga like よつばと！ won’t contain a lot of (if any) grammar it doesn’t get.
EDIT: I do notice we’re in the wrong thread 
questions like these are better suited to the Short Language Questions Thread or the Short Grammar Questions Thread