I am a bit curious on this one. I currently work 7am to 7pm, on a 2 weeks off schedule.
During my work time, I train at 6:10-6:30 after breakfast, I noticed I am much sharper in the mornings than after work. With this I have begun training on ML in mornings and IAM for 5 min words at nights. Note, that I excercise around 45 minutes prior to breakfast, as this may influencing factor
When I am home, and not working, my performance remains relatively constant.
I typically train 3 sessions, 45 minutes long when I am not working, typically afternoon, around 5pm and the evening. My performance was typically consistent with no variations among different training times.
My belief is that information/stress/brain use at work is causing interference/fatigue on my night time performance when I am working.