i had a new engineered wood floor installed during this past month (in cold temperatures) and have noticed quite a lot of gaps vertically and horizontally. the wood flooring store's owner says that it will expand with warmer weather. the installers have filled in some of the gaps with a wood filler that does not harden. i went to two other stores and both told me there should be no gaps as such, and that it was poorly installed. help should i be satisfied with all the gaps being filled in with the filler?