A904 not downshifting, dark film in bottom of pan

Recently rebuilt trans and removed the pan to inspect the linkage movement. Car was also not downshifting when throttle is wide open but throttle kickdown is connected and appears to be working. Dark film at the bottom of the pan and I've only driven about 40 miles. Transmission was fried before rebuild so possible some of that material came from the torque converter. Thoughts? Other reasons why it will not downshift?

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