-might be mentally ill (exascerbated by the religion) and the stress causes a sort of "bi-polar" tack with the 'truth". for example- a young woman might leave, become 'worldly" and get sexually promiscuous, gets pregnant, gets scared, goes back. makes brings her boyfrind/hubby along. (who as the punk fella described might be total social misfit who finds a 'family" in the knigdom hall) becomes very pious for a time, then leaves her spouse and becomes worldy again. lather rinse repeat. my old congregation had one gal, the kingdom hall was literred with her ex-bo's.
Oh boy! I knew several of these!!!

In the situations I remember, the beau would end up being a "perpetual Bible study".....in other words, he KNEW it was bullshit but remained "in" just enough to keep the pressure off.

Piggybacking on this---I know everybody remembered the "Settle-downer Sisters"........female members who grow up in the congregation, leave for a life of non-JW freedom, and end up back in--very much like you described. I say "Sisters" because I hardly ever knew any young men to come back.