Nice that we got this far.

The problem you describe is almost certainly caused by not implementing the toggle code properly: This is a bit in the signal, T, that flips ("toggles") between 0 and 1. That way it is easier to distinguish between "long", repeated presses and multiple presses. Some devices check it, some ignore it, some forgive after a timeout period.

The codes I generated all have toggle T = 0.

There are two ways to address this: either let the remote take care of the toggling, or keep every signal in two versions, with T = 0 and T = 1. Needless to say, the first solution is preferable. A Pronto "should" accept the "short form", 5000 0073 0000 0001 0004 0033 for "Video". Please try this again.

To try with, here are both versions of "Video":

rc5_D4F51T0: rc5 Device: 4 Function: 51 T=0
0000 0073 0000 000B 0020 0020 0040 0020 0020 0020 0020 0040 0040 0020 0020 0040 0020 0020 0040 0020 0020 0040 0020 0020 0020 0CA8

rc5_D4F51T1: rc5 Device: 4 Function: 51 T=1
0000 0073 0000 000B 0020 0020 0020 0020 0040 0020 0020 0040 0040 0020 0020 0040 0020 0020 0040 0020 0020 0040 0020 0020 0020 0CA8

And by all means, install IrScrutinizer yourself...