Just seconds into my ride today. All 800-1200 watt awards popped up. Using a TACX smart trainer. At my age, I would be lucky to earn the 800 watt achievement at any time.
My guess would be that you had a (short) connection problem. No power signal for a short period, after which Zwift tries to catch up. I had one, in which I did 2000 W for 2 seconds…
Unfortunately you can not correct the data as far as I know (to much chance of abuse I guess), so the numbers are there to stay…