How to completely delete sleep data (as the tracking is very wrong after the latest beta update)?

Ever since the last beta firmware update, my sleep tracking data is completely off - it tells me I am awake for 3-4 hours every night. Consequently, it gives me sleep hours of also 3-4 hours every night (as opposed to 8 hours before the update).

A few days with such wrong sleep data was fine, but now it it seriously pulling down my average sleep data, making this data completely useless.

So my question is: Is there any way to completely delete the sleep data for these wrong nights?