If the screen hasn’t been cleaned ever, that could be it. Mine had some gunk on it at 50 hours, most of that leftover from the factory. Gasket material is common in there.
Also you might want to see if your fluid gets foamy when you're at temp and having a problem -could also be some temp sensitive sucking up air from the suction. Another possibility is the suction charge pump on the left upper side of the transaxle