To make my comment above a little more specific, the version of bcmwl-kernel-source that does not cause interference in my tests is 5.100.82.112+bdcom-0ubuntu3 (the last release for quantal).
To make my comment above a little more specific, the version of bcmwl-kernel-source that does not cause interference in my tests is 5.100.82. 112+bdcom- 0ubuntu3 (the last release for quantal).