Yeah very understandable. I once had a huge year training, did nothing wrong and didn;t improve, then I backed off training and beat my personal best over the 4km distance.its not the time im disapointed with, its n2b. its just ive done a heap of hard work in between our 2nd and 3rd TT and somehow i maneged to go backwards by 3 seconds. thats whats disapointing.
Might be you are doing too much work? Are you lifting heavier weights? That has an affect on body composition which makes it harder to run.