Mirage
Is it doing this right out of the house?
One of ours was doing that once, and we found a small piece of broken target stuck where the target rests before thrown. Or it may have been on the arm under the rubber.
Either way, we cleared it, and flight was normal, even when we had a cross wind. Sometimes with a crosswind, the target will curl off one way or the other toward the end of it's flight.
Also, sand the arm rubber to get a bit more spin on the target. That may help also.
Cold weather makes them do funny things.