The long Pronto Hex strings are exactly what one would expect assuming that the short Pronto Hex strings are perfect. (So the long ones didn't suggest any improvement of the short ones).

I'm not sure what one might hope for in adjusting the duration. But .01 through .10 is not an interesting range. The duration is always at least that long. The interesting range would be .2 through .9. Also those long Pronto Hex strings were learned in a way that means the Pronto won't know how to correctly adjust the duration. Adjusting duration is more meaningful with those short Pronto Hex strings, but I still don't see how it could fix any of the symptoms discussed here.

I understand why the long Pronto Hex strings malfunction as described earlier. But I still can't think of a second possible explanation for the malfunctions described for the short Pronto Hex strings. Are you really sure each short Pronto Hex string is the only action on each button's action list? ANY other action (not just other actions that send IR signals) would change the timing rules and could explain the symptoms.