the access you show wont cause overflows.
as i said, Id need to see your allocation of the array. I can only guess for some reason, the attribute is not applied properly. (it defaults to SRAM, so if its wrong, this would be expected)
EDIT: its probably easier if you upload a test patch with the relevant object embedded. then we can see what the issue is/what you are trying to do.
(minimal patch, with just your allocate/read/write nothing else )