MK133 problem with locking out other buttons

Hello. I have just finished the MK133 kit. One small problem. When SW4 is pressed the other buttons are not locked out meaning a second LED can light up. This only happens for LED4/SW4. The connections look okay and none of the diodes are reversed. If anyone can provide some possible things to look at it would be greatly appreciated. Thanks.

Most likely T9 and/or D6 are not doing what they are supposed to do.
Check and/or replace.

Thanks! It turns out I installed the transistor backwards…its working great now.