Thanks for reporting, but I can't reproduce this bug, everything works fine on my side with Factorio v0.17.15 and Factorissimo2 v2.3.1. Can you please tell me more about the exact issue you're having (include screenshots) and what exactly you did to create it?
Intentionally I did nothing, calmly played. The problem most likely lies in port throughput. When you connect a blue belt, the port skips 6 items every 10 seconds, the red belt passes 18 items, and the yellow one works as usual. https://www.youtube.com/watch?v=nsQYaOwbjvo&feature=youtu.be
You installed a mod that makes your belts faster. Belts running faster than 1 item per second per lane aren't supported by Factorissimo2. Instead you can use chest connections with loaders.
