TACX FULX S - LOOSEN UP IN THE MIDDLE OF WORKOUT

Hello,

I am making my own workout and afte 30min ~ my watt power dropped and and return every 30-40 second. 

for example my workout is set to 300watt at 85rpm for 2 minutes and when i get there it drops to 100watt same rpm even if I swift gear will full power it keeps me to 100watt, after few seconds it gives back the resistnas to 300watt and then back to 100.

I had to stop the workount reset the program and start all over with new workout.

I use tacx ant +  , hrm pro , tacx flux s smart, desktop app (windows)

thank you in advance.