Hi!
One option is to quiz yourself on 3rd roll positions in my backgammon database. Enter 3 in the move number field and then set an error threshold that you prefer and off you go:
You could also take it further and mark the "All wrong answers match error threshold" which would mean that there is only one correct answer and everything else is an error.
I just created a challenge "3rd roll challenge" where all wrong moves is a -0.180+ error so any incorrect answer is worth studying closely.
Considering that the errors are taken from international tournament matches there is likely to be a fair amount of difficult problems to try your skills at.
With a private database and thousands of your own matches uploaded you could quiz yourself on all 3rd roll problems where you have made the wrong choice in the past.
TP