after updated all the 5 packages below to new version, this issue seems fixed in my quick testing.
nvidia-driver-390 (390.77-0ubuntu0.18.04.1) gdm3 (3.28.3-0ubuntu18.04.1) ubuntu-drivers-common (1:0.5.2.1) nvidia-prime (0.8.8.1) nvidia-settings (390.77-0ubuntu0.18.04.1)
after updated all the 5 packages below to new version, this issue seems fixed in my quick testing.
nvidia-driver-390 (390.77- 0ubuntu0. 18.04.1) 0ubuntu18. 04.1) drivers- common (1:0.5.2.1) 0ubuntu0. 18.04.1)
gdm3 (3.28.3-
ubuntu-
nvidia-prime (0.8.8.1)
nvidia-settings (390.77-