The transmitter board looks like it might have a bad IR LED.
There should be two green LED's lit and the center one is off. Usually that means that one of the IR LED's has failed. If you pull off the transmitter board and take a look at it with a phone camera, you are likely to find that the 4 on the right are not lit.
Unplug the board and check each LED with a DMM set to diode check. Red lead to round pad, black lead to square pad. If the LED is good, it should give you a reading of some form. If it is bad (blown) it won't read anything. Also, if you find one that reads 0 or if you DMM beeps at you, it is likely that the LED shorted out (and then possibly cause one or more of the others to blow.
Replace any that are bad.
Hope that helps!