[2020] Need help: Traffic question - Odd Behavior

Cars cannot enter an intersection if they cannot make it out, so they are stopping to wait for the car in front to exit the intersection and make room for them on the other side. This happens pretty often when you have several intersections close to each other like in your 2nd screenshot.

You can solve this by minimizing the amount of intersections that close, so that there are fewer situations like this. Or you can use TMPE to change the intersection rules, so cars can enter an intersection even if it's blocked. Keep an eye on them if you do the latter though, as that might also cause more problems in some cases.