Found this in the GUI, see TestCentric/testcentric-gui#337.

There are a number of outstanding issues that may be related, but I decided to create this one anyway since it's specific to the force argument being true.

When we cancel with force false, everything works as expected. All ongoing tests and suites terminate and signal completion. The run is signaled as complete.

When force is true, the tests are aborted and signaled as complete but all ongoing suites are merely abandoned. No event is received for them so they appear to still be running. No run finished event is ever received.

Note that our existing tests around this all pass because the run is actually aborted. It just doesn't look that way to any runner that relies on event notifications, which is why I referred to an "apparent hang" in the title.

Existing issues, which may be related to this: #2947, #2282, #166 (five years old!). #166 is assigned to @oznetmaster, the others are unassigned.