The problems seem to be fixed following installation of this package:
linux-modules-extra-4.15.0-20-generic:amd64 (4.15.0-20.21~16.04.1)
The problems seem to be fixed following installation of this package:
linux-modules- extra-4. 15.0-20- generic: amd64 (4.15.0- 20.21~16. 04.1)