In runs, the cadence values do not seem to be sampled from the counter regularly enough, and the steps per minute count is almost random, with some "stuck" values and runs of zeroes. Here's an example:
This is only if you use the internal step/cadence sensor. With an external RD Pod or HRM Pro the values are what you'd expect. This is a change in behaviour since version 11.12.
I have already provided several examples of this to Garmin-Kevin via upload/email.