Transmission not engaging?

1997 Ford Explorer Sport. Its an automatic but Going from any gear upward, car hesitates, rpms rise like im in neutral and then finally kicks into gear. I have slight oil leak but have no idea how that would affect anything unless there is oil on the transmission. Please Help.

Check trans fluid level at dipstick with it running in park.

Get codes checked for any MLP or gear selector codes.
Have had MLP sensors make ford autos go into neutral for 3-4 seconds between shifts. Scary.
MLP sensor is on side of tranny and easy to replace and less than 90.00 from dealer I believe. Can be cheaper elsewhere. Salvage yard should have a good one pretty cheap.