Ruud uprl-036jez is tripping on

Question

ruud uprl-036jez is tripping on high head pressure. Indoor coil seems to be clean, filter is clean. ref charge is good. Indoor txv was replaced. Fan is on high speed. Hooked up to a 10yo olsen direct vent oil furnace with direct drive blower. This coil is on the return. I have another hp, same model number that is on another oil furnace buts its on the supply side and its doing the same thing but doesn't always trip. The pressure goes really high and then it just drops back to normal. Neither units had problems in cooling mode. I think it may be the txv outside.