Distributor seems to jump out of timing?

halifaxhops said
Mopar Distributor Shaft Lengths
Mopar Distributor identification guide by measuring shaft length, measured from mounting surface to lower end of distributor shaft.

Mopar LA engine – 3.875”
Mopar B engine – 3.5″
Mopar RB engine – 4″
–
Chrysler 331/354 Hemi – 4.25″
Chrysler 392 Hemi – 4.5″

Thanks Hops, as I was going to mention the different length shafts, but didn't know the specifics that might allow a shaft to partially seat.
Then I thought that if it was a shorter shaft it wouldn't engage at all, and if it slipped at all it wouldn't run anymore at all.