[sdperham]

You're on to something!

There was some confusion whether the transmission shop did, or did not, intend for me to pull off the shifter housing assembly to fill with gear oil. I assumed (probably incorrectly) they already installed the forks correctly then installed a gasket and "set" the housing.

Now I bet if I pull the housing, I will see the forks aren't engaged in the grove like you suggest. I'm going to pull the housing now and confirm if this is the issue. If so, I will reinstall the housing with the forks in the grove, then install a new gasket.

This would be a great solution and outcome (and lesson learned). Fingers crossed. I'll repost with an answer.
Thank you!!