BTW, the MCE protocol includes a "toggle bit" that typically stops a learned signal from working when you use the exact same command twice in a row. The signals generated by MakeHex act like learned signals.

Assuming these basically work, please test whether you have that problem.

Some buttons that are frequently used multiple time in a row, such as Up or Down might or might not have the toggle bit ignored (so they might not get that problem, even if the basic design has that problem). If those work twice in row, try something with a toggle behavior:

Is Open tray the same command as Close tray? Assuming, so and assuming a toggle bit problem, I would expect that you couldn't open and close the tray with two succesive presses with nothing else between, but could close the tray if you press some other command after open and before close.