Kubuntu 18.04 LTS, x64 (nvidia-driver-390)
NVIDIA GeForce GTX 1080
2.80, 4b7596ec914e, blender2.8, 2019-01-05
Short description of error
Perhaps this is not a Blender bug, I could not understand. I can not insert a face at the bottom of this model, on top of the model, the face is inserted perfectly. The essence of the problem can be seen in the video. The file with the model is attached.
Exact steps for others to reproduce the error