kaihengfeng, I tested with linux-image-unsigned-4.15.0-21-generic_4.15.0-21.22~lp1768292_amd64.deb and was unable to duplicate the issue.
kaihengfeng, I tested with linux-image- unsigned- 4.15.0- 21-generic_ 4.15.0- 21.22~lp1768292 _amd64. deb and was unable to duplicate the issue.