1953 AMI E 40 not rejecting at end of record

I've been getting my feet wet on 50s AMIs with a Model C and a model E.
I've gone over them tooth and comb, and had them both working last
week.
Today I went to type up title strips, as the owner is auctioning them
off Saturday (moving to California from mid-west area).
The E is finished playing the record, and will not reject by these
means:
1)hitting reject button
2)shorting across reject contacts (microswitch actuated)
ALL fuses are good, and NOT blown. I tried turning gripper arm motor by
hand to return record to stack, thinking gripper arm motor may be
jammed or in a bind, but turntable continues to rotate.
DC switch on rear of junction box is in on position.
I've come so far on these two jukes, and thought I had both running
last week (I did!, until this morning). All of my AMI friends tell me
they're the simplest to work on....but I'm missing something. Any ideas
what to check? It HAS to be something simple, but what? I'm better at
Seeburgs and Rock-olas, and could find little on this symptom in the E
manual (e-80 and E-120, not E-40), or in the Dr. Know-it-all book on
AMI's by Harold Hagen.
Dan Colabuno helped me by phone last week, but it had a blown fuse
then. Now the fuses(all 3) are good. What gives? Thanks, Rob

I think I may have figured this one out on my own...with the help of a
friend. I had to replace the four wire cable (very badly deteriorated;
crumbly and brittle) that runs from the front of the mech around the
left side to a four prong plug that plugs into that relay/junction box
with 3 or 4 other plugs. I may have a cold solder joint that worked for
awhile. I'll check it later today. Thanks to all who were thinking of
writing in an answer. Rob