Weird.
Are you using PowerMatch?
I’ve got a Kickr 2017 direct drive, and using TR PowerMatch with Stages LR crank-based power meter. My ftp is lower than yours, VO2max intervals at 294W target versus your 348W: Power Match seems OK but not great - tips and tricks I'm missing? - #8 by bbarrera
Although not needed due to PowerMatch, I usually stop after 10 minutes and do a Kickr spin down.