Im encountering this very often lately. In the image you can clearly see that Alioth 1 is colonized but if you check the build order it says its still no ready...no matter how many turns pass by it is stuck there, also I cant cancel it. It happens with almost anything. Havent encountered it when building a ship.  Also sometimes it denies to build anything else and its stuck there making the system useless , other times I can simply put stuff over the bugged build order and they will be build without problems. Its completely random, I tried to figure out if im doing something wrong but I had no success it just happens on its own. When it completely bugs a systems build order I become unable to build anything but ships in that system. I cant find the right way to reproduce this. It just happens on its own. I was messing around the debug menu the first time so I started a new game without cheating or doing anything i shouldn't be doing. It still happens.

Anyone else encountered this problem?

oops wrong forum...this site is confusing , hope a mod deletes this. Sorry