I am having exactly the same problem, what i do is i don’t le the raid pass the 8 tb marker because it always fail with this amount of data.
G speed es pro is the worst purchase i have ever made, novody knows what is the issue and GTech Atto and apple just throw away the ball.
My advice is don’t G-SPEED eS PRO, go with the promise 16 TB thunderbolt Raid,