Will not go when in drive unless winter drive button is pressed. Reverse works

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Reverse works fine but won't go forward unless winter button is pressed. Also transmission slips sometimes when going down the road. I changed the fluid and filter but still no good. When I put it in drive it will move very slowly until I hit that winter button it takes off in 2nd or 3rd gear then at 20mph the winter goes off and the car drives fine except for the occasional slipping.