I had this problem with the same strain last year, it started to flower and reverted to veg , I later flipped lights for the photos to flower and it then flowered, spotty genetics on the blue mammoths for sure
don't transplant auto flowers ever it slows growth and can cause them to not grow much because their vegetative time is already so short, next time germinate the seed in the final size container of soil that you want it to be in you will see much better results, good luck with your grow!