with a West Coast offense.
The WRs are supposed to read their keys on the defenders, and based on their pre-snap reads the WRs make a decision on what variable of their route to run. The QB is also supposed to see the how the defense lines up and make the same decision that the WRs make.
So if the Slot WR reads the D and says "based on my read I am supposed to cut outside", but then the QB says "based on the D guarding Slot WR he is supposed to cut inside" we have some of the mistakes we have seen.
Both players are reading the D or their Qs like they should. It takes a lot of time to develop that kind of chemistry. Just look at Rice and Young.