I have three suggestions.

1. Replace all 2222 transistors and their base resistors with a single ULN2004 chip.

2. Replace 74LS138 with a HC138 type.

3. Add an NPN to drive the PNP transistors since there is current flowing from the emitter-base junction of each PNP transistor. I had this problem too. Put res. from +12 to base of PNP. Then res. from PP base to collector of NPN. Emitter of NPN to ground. Base of NPN with res. to driver.

Ioannis