I guess the output of toggling switch UP is affected by DisableInterrupt() and EnableInterrupt() calls in the event handler - it most likely causes the other interrupts to be ignored/missed.
I would recommend you to remove those Disable/EnableInterrupt() calls; and also change the interrupt trigger to InterruptEdgeHigh, so the button release event is not generated (you can add it back again later, if you need it). Also, apparently the switch bounces, so you'd need to implement either hardware or software debouncing (or both).
You can make the circuit a little bit simpler by switching to pull-up resistors, because you can enable the built-in ones (in the InterruptPort constructor); then you'd need to use InterruptEdgeLow instead.