Advice needed Fatigue vs Fresh HR and body recovery

Hi Everyone,

So quick run down. Last tested FTP 3 weeks ago was 296 ive been doing high volume sweetspot/threshold with some added zone 2 hours. At the end of this 3 weeks of volume my fatigue and form as very high/low 130+ and -40/50 however i felt very strong and comfortable. My HR was low and my numbers were high. i.e. high sweetspot HR for 320 watts for 7 min repeats. (Elephants +5). I had 3 days recovery. 1 petit and 2 days nothing/ at work. Then I tried Carpathian Peak and barely lasted 5 mins before my HR was through the roof and my legs couldn’t handle it I am at altitude so when i go over a certain HR i can only go so long up here.
Basically I want to understand the factors of this and why I always perform so much better on the bike when i am heavily fatigued. Im not ill, Unfortunately don’t track HR variability or resting. This also happened after last training period where i went into the ramp test very fresh and my HR was overly high compared to the training week before. Has anyone else experienced this or got answers?

I don’t know the reasons or biology behind it. I always do an opener the day before, before a longer or harder effort. Some people call it activation.

Basically Zone 1, then a set of 3 - 3 min @ 95% with 2 in rest between intervals, then 3 - 2 min @ FTP with 3 min rest between, then 3 - 1 min @ 120% with 4 min rest, then 3 - 30-45 seconds at 200+% with 5 min rest. Then wind out the workout at < 50%.

Next day, good to go.