Whilst your movement 'in the basement' may be slow, that is only because you are fighting the resistance. The muscles are still firing fast. If you were using a lighter weight, and purposefully lifting slow to fatigue the muscles (a bodybuilding technique), then, from a Power lifting perspective, you would be doing it wrong.

If thr weight 'felt like nothing' however, you do have to ask yourself why that first stage or ascent in the rep was such a grind?

Every positive movement in a rep should be just that - positive. Strong, controlled and full. If the rep happens in 2 stages (small move to sticking point, grind through that, then finish strong), there is a case for lightening the load to create a single strong movement.
Don't let the door hit ya' where the good lord split ya'