Please view and follow along with the pictures below to properly unjam your Mars/MEI validator bill path.
Push up on metal bar on bottom of validator
Carefully start pulling out the bill path while pushing up on the metal bar. Some models are harder to pull out
Slowly pull bill path away from validator to expose jammed bills
Pull the bill path comepletely out and removed jammed bills. Then, carefully insert bill path back into validator until metal bar clicks in place.