If your power value changes unexpectedly while running at the same pace across runs, or power is at an unexpected value when you view your data in your Stryd account, it is likely the weight setting on your Stryd pod changed.
One example of how this can happen is when Stryd is never paired using the Stryd app on the phone. In that case, Stryd will keep its default weight setting of 70 kg. If you later on pair with Stryd, for example, to update the firmware, the weight will reset to match the weight in your profile which may be different than the default.
To address this problem, you need to update the weight setting on your Stryd pod with the Stryd mobile app.
Note that it is currently not possible to recalculate power of runs with incorrect data.