sounds like the pot may have a dead spot in it. When it does not want to accelerate will it move if you smash the pedal? If i does that makes me believe the pot is bad. The transmission that is a weird problem ive never encountered it but it either may be a glitch in the shifter assembly its self or in the plate in the trans.
1982 300D Turbo (Mom's)
1993 BMW 525I (Dad's)
2001 Vw Golf (Brothers)
2002 Nissan Ser SpecV (Im the Black sheep lol)