This isn’t a bug. LayOut’s dimensions are now associated with the model. Red boxes around the dimension text indicate that they need to be reconnected to the model. Right click on them and choose Reconnect. You can select multiple dimensions and reconnect them at the same time, too.
Now, if you change the length in the SketchUp model the associated dimension will get updated when you update the reference in LO.
See the Release Notes for LO2017.