[Rockhounds] 18 inch saw has a problem

[rockhounds at adelphia.net]

MY OLD 18 inch saw stripped the shaft a while back. Had it welded/repaired and now finally got it back together. When I cut a rock now the saw has a gap of about 3/8 of an  inch at the end of the cut  yet is still in contact with the blade at the point the cut started.
At one point the whole delivery system was taken apart.
The saw is similar to the old convington type of design with the screw and saw powered by one motor.
The blade looks to be true.
Any ideas on the problem?
I attached 2 photos


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