I agree that you should clean all the boards. I use deionized water, dish soap and a soft brush. After thoroughly brushing and cleaning of the dirt, I rinse the PCBs with deionized water many times, blow compressed air (especially under ICs and components) and leave them for about half a day in the sun (the next day I check them and blow air again before putting them back on).
I wish I could help you further, in my place I have a chip tester, a soldering-desoldering station and I can possibly find locally a new uln2803a and a socket for it... But you need these skills and tools to test and replace an IC.