“If scripture isn’t the only infallible source for what Jesus and the apostles taught shouldn’t it be easy for Catholics to show another infallible source showing the apostles teaching the assumption of Mary?”
Oh, so you’ve already abandoned any attempt to show sola scriptura is Biblical, right? Thanks. I proved my point.
No, I haven't. Catholics are the ones who claim scripture is not the only source for doctrine. Its incumbent on them then to show any other infallible source. We know that infallible scripture shows:
Search the scriptures to determine if what is being taught is true.
If someone teaches something as doctrine that the apostles didn't teach to consider that teacher accursed by God.
So until Catholics can show another infallible source that shows the apostles taught the assumption of Mary we can be sure that the teaching is false and the teacher of that is accursed by God.