Inexplicable drop in w/kg

Last night I rode the Everything Bagel route in NYC. Over the last roughly 0.2miles, while working hard to finish well, Zwift was showing a reasonable and decent (for me) power around 240W, but my W/kg, which should have been 3.6 at that point, suddenly dropped to 1.1 and stayed there until the finish line. It’s hard to tell, but the upload to Strava shows a drop in power at the very end of the ride that might correspond to 1.1 W/kg*66 kg. Is there any way to diagnose what happened there? I’m pretty sure I didn’t accidentally gain 150 kg at the end of the ride. Setup has a Kickr v5, Apple TV v4, but this seems like a Zwift issue.