A couple times while speedrunning the game, I have encountered cubes that I couldn't pick up. I have encountered two in first area of the game, and haven't played further to see if it happens in other areas (mainly because it prevents me from getting out!)
Here is video of one such occurrence. I can't pick up one of the blue cubes at the end, even though I am clicking directly on it and its neighbor works just fine.
I have also encountered this bug multiple times (I think twice?) on the red cube at 0:32 in the video. Restarting the game seems to sort things out.
Windows 10 Home version 1903 (build 18362.10024)
Intel Core i7 6700K @ 4.00 GHz
Nvidia GeForce GTX 1060 (6GB)
I just realized that my speedrun timer covers up the build number at the beginning of the video, but I was on the latest Epic Games Store version at the time I encountered this. (From William's Twitter, I believe it is 184.108.40.20675.)