Removing it and then placing it again doesn't fix it.
Fast or regular underground belts on the same place does work.
Replacing the Plastic Bars with something else makes the belt do its job. Just not for Plastic Bars.

Save game here
Same here , express underground belt do not work anymore after 0.9.1 update.elkar wrote:I have quite same issue, but it doesnt matter what materials I have on the belt, express underground just doesnt work for me. See the pic, when I replace it with yellow or red belt it works instantly.