If straight bars, then almost certainly I will say that you are not keeping your wrists straight. You are letting your wrists roll downward and your hands are angled upward in the same position that gives computer users carpal tunnel when they stay on the keyboard too long.

Just like for the keyboard use, the top of your hands need to be in the same plane as the top of your forearms. No bend in the wrist!

Get some other bars too! Anything but straight bars.