LEDs LD1 through LD4 are not lighting. The rest work perfectly.
Check these led’s there polarity and the solderjoints.
Check also R1.
I had this exact same issue and since it was only my second mini kit, I figured I missed something or did something wrong. After reading this thread I went back and checked all my solders to include R1 as suggested. Still had all LEDs flashing properly except LD1 through LD2. I checked the polarity on every LED even though I know I was very careful about thier placement and none of the LEDs were mounted reverse polarity. I then tested each LED with my multimeter set on diode function and finally found that the LED in LD2 was not functioning. I desoldered the points to remove the LED and retested it with the polarity running in each direction to be sure and it wasn’t working at all. Luckily Velleman had supplied a single extra LED and as soon as I swapped that LED into the LD2 location, everything worked fine. All LEDS in both rows lit up and flashed alternatively. So if you run into this issue and rechecking solder points do not help and you are sure you put the LEDs in with the proper orientation for polarity, I would start testing each LED that is not working in the run with a multimeter set to diode and you may find the issue.
I hope that helps someone else that is new to this stuff like me.
Sincerely,
PurpleHeart91 (Jerry)
Cpl. Medically Retired USArmy