Pulsating resistance

I installed the Zwift Cog onto my Hub and started using Play controllers last week with virtual shifting. Now the resistance is very uneven. It surges/pulses every few seconds to the point where it is essentially unridable (especially high-resistance scenarios like climbing). It is also seems to be throwing off the RPM estimates. All firmware and apps are up to date. A screenshot for a few minutes of the Strava record is attached for reference. Any advice would be appreciated. Thanks!