I just completed WO2. No issue with ERG on.
I have my base resistance set to about 50% for free rides. Zwift do remember that value so all free rides has the same resistance.
Free ride blocks does not follow the route profile. There is a manual edit you can do to have it follow the profile.
If you look at the WO2 .zwo file you will see the free ride block is defined as
<FreeRide Duration="20" FlatRoad="1">
“If you alter a .ZWO file that contains a “freeride” to remove the flatroad=“1” option your smart trainer will go to sim mode (follow the route profile) in this portion of the workout.”
check out Shane’s Flatroad=“0” hack.