The band applies in 2nd gear only. The front clutch applies 3rd gear. There will be your problem. Either the front piston seals are leaking or the stator support rings are an issue. The support rings seal the forward drum to the input shaft. This is the oil feed path to the front clutch piston. Pay close attention to the rings. If they are worn on the sides the grooves in the stator support will be worn. Replace the support or it will happen again. The clutch fibers and steels will be damaged as well.
Doug