As someone who accidentally ran an engine with the counterbalancer chain full slack, I can attest that you can make it approximately 30 kms before the chain snaps, and the engine grunches to a halt, making expensive noises.
Teardown revealed the end broken off a doohickey torsion spring. I'd done an oil change and doohickey adjustment day before, in prep for a trip. ...ran it after the oil change, thought it sounded a bit different, but ignored that (silly me).
One theory, is that it's possible to nick the spring, if you're using sharp edged needle nose pliers (for example)... or that the edge where the doohickey contacts the spring can wear into the spring - I slightly radius that contact point now when I install a doohickey.