If you divide your watts by w/kg you will see the ride weights they give are all over the place:
5s 64.2kg
15s 68.0kg
1m 78.5kg
3m 72.6kg
5m 78.8kg
12m 78.3kg
20m 75.8kg
30m 84.7kg
Nothing like you real weight of 85kg other than 30min. I would expect a few minor rounding issues but not this many. I think all of mine are within about 0.1kg of the ride weight in force at the time of the PB.
I think something is going on with the calculations and it might somehow be related to letting somebody else ride at a large weight difference - but I don’t know how or why.
Link below is very similar. I think you will need Zwift support to look at and sort out.