Correct me if I'm wrong, but you also have the auto.sh file that runs after boot?
#!/bin/bash
xhost +
echo $DISPLAY > /home/user/.display
lxterminal --command "/usr/local/bin/startminers.sh"
I think this might help Kermee debug the problem, I'm having it too, whenever I've seen xhost + used it is usually always after an
export DISPLAY=:0