my 93 teg does almost the same thing.

I do believe, at least on mine, it's a preventative measure there on purpose. Reason, I push in the clutch while coasting at about 40mph... downshift to 2nd, clutch still in... move it to 1st... apply light pressure as if moving to first and waiting for it to let you. Once the mph get below a certian amount it just opens up and lets it fall into 1st. I think it's somewhere under 10mph... I never really took notice.