UWP CommandBar SecondaryCommands KeyboardAccelerators
SecondaryCommands KeyboardAccelerators in a CommandBar only work until the SecondaryCommands menu is opened, then when closed they stop working. This has been tested in 1809.
Blake Pell commented
I saw somewhere that this was being fixed in the April update. It's super annoying and if you attempt to use keyboard accelerators at all with say, a menu, it's apparent ASAP. How this made it to production is astounding.