Perceptible room echo

I am told by the quality control team that there is some room echo in these recordings. For me it is difficult to appreciate, and I always record in the same space, so I don't understand very well why, if most of the times the sound is perfect, why some other times they detect this problem.    I have acoustic panels on the walls and a thick theatre stage curtain isolating the space from the room I record in. Also, I use Shure professional anti-pop, for my microphone, Shure Sm7b,

These are the projects I have been told about that present this problem. how can I improve?

1. https://bunnystudio.com/projects/880737f5-6244-460b-ae11-9c630c70a918/
2. https://bunnystudio.com/projects/6a04c15e-63b2-4c15-8c35-458785013109/

3. https://bunnystudio.com/projects/0643e8fa-c476-48de-9de3-ec09d01db428/