in general the seeming contradictions in bible are in 3 categories.
when 2 versions are not identical, still the details are the same even if different words just adding a second witness not the same one copied twice.
example story of hezekia in book isaiah and in book kings.
b when a version has different details, still each version is adding to the other, while preserved only one event not two events. for example jesus shirt was red and jesus shirt was purple means he had both colors but each author mentioned one whi hever later responded to earlier version the additional detail for example someone read book mark so rewrote his version with more details than mark.
c rarely details seem to conflict. for example isaiah 65 said "a new heaven and a new earth" but eccl. said 1,4 the world is permanent?
but that is only due to the translation not in the original text.
source a, eccl. 1,4 hebrew lolam. differs from psalm 145,1 "lolam wa'ed" the added word stretches a long time to forever so the translation forever is not for the word lolam alone in eccl.
source b, the use in exodus 21,6 the slave will serve lolam... but not more than his lifetime just a long time. it doesn't mean his soul is a slave because didn't add wa'ed. in contrast to praising god added word waed teaches the soul will praise even after death.
source c isaiah 65,17 a new earth. peter probably refered to this part of isaiah.
so the idea earth lolam is not forever, as English translations because lolam is less than the phrase lolam waed, just a long time like by the slave until the trumpet of freedom specified in jubilee year in leviticus.
so the source is the hebrew of eccl. and the comparison with the same word used in psalms and exodus as above so no conflict to isaiah.