it gets bad at 4.45 pm
sometimes it can be 9pm when you get out.
a few months ago i went into gib for some pie and left at midday and got back in the house in Sotogrande at 9.45 pm.
being stuck at the border is part of the experience i think.
if you leave at 8pm you will have no problem.
just live with it and use the time to listen to some local gib radio or something because its very unpredictable.