BP still has scratches on belly why?

[CakeLike]

Unfortunately, you're the only one who can see & fully investigate his enclosure. You obviously didn't find the cause the first time, so I suggest you keep looking. Could there be a chip on his water bowl?

No his water bowl is very smooth.
I just can't get my head around how other keepers keep their snakes inside natural habitats with many rough surfaces, woods and stones and I really try to keep sharp edges out but I can't get it right.