I have 6 tortoise: 4 adult russians and 2 small (4-5"
leopards. I've also raised several russian hatchlings.
The russians live outdoors where they have rocks and logs to crawl over and fall off of. Which they do all the time. The hatchlings had a similar but smaller indoor setup where they crawl all over things.
The leopards have a 7 square foot enclosure which has tall sides. They often push each other around and spend alot of time under the basking lights.
I've never come home at the end of the day to find any of them lying on their backs. When I do see one get flipped over, I can come back in a few minutes to find them upright again.
I bet every tortoise ends up on its back at least a few times during its life in the wild. If they couldn't deal with it, then they'd all be dead before they were a year old. Of course there are some that fail due to an unusual situation or physical weakness.
Make sure the tortoise has a firm substrate in its enclosure. Loose dry sand, coco fiber, wood shavings, etc., would provide little for the animal to hook its beak or claws into when it is struggling to get upright again. My outdoor torts are on a mix of hard clay and grass. My indoor leopards are on newspaper, and the indoor hatchlings are on a firm mix of soil and sand. Make the area under the basking lamp a flat rock, tile or slate.
If your hermann's is incapable of flipping itself over even in the best of circumstances (and give it a few minutes - it's not something that they can do instantly) then maybe it is weak and needs extra attention.