Add some additional AFT+4 fluid to the transmission. Bring the level up between 1/4 to 1/2 inch above the full mark on the dip stick when at normal operating temperature.
This is a common issue.... If this does not cure the problem, you may have to consider having the front pump assembly replaced in the transmission.
There are parts in the front pump (plungers & bores) that wear over time and cause problems...

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