You're welcome...I'd definitely drop the pan to see what is at the bottom and assess the condition of the fluid before buying another trans or doing any major work (or even drive it a bit more to see if you can duplicate the symptoms and if they are getting worse....There's an outside chance it could be valve body but since you have delayed engagements in both reverse and first gear, it's more than likely your applied elements are stressed/heavily worn. A clogged filter can also be the culprit; which if it's partially clogged could present with delayed engagement issues due to a combination of really thick (cold) fluid and partial restriction in the pick-up. You can cut it open and see what may be inside of it when you do the service.It's always something, and it's often a struggle. I just went out for a bit and it acted as though it never had an issue. Please don't think I doubt your advice. I'm sure you've forgotten more than I'll ever know about the magic box. Your video will be a big help when I start looking for a used one.
Odds are it needs a rebuild, but I always like to either obtain diagnostic evidence or have it simply straight-up fail in an unmistakable, unambiguous way before condemning it.