Tried validating source files. no change in them.
You mean that you are always loading the same files? I don't think so.
The error message makes it very clear that the file you are reading now does not match the expected format.
Yes, I see that you have checked the file, but the error message does not lie.
If you want more help, we need to see the statement you use, and we also need to see the file that fails. (Yes, I understand that you may not be able to share the file publically, but I'm only informing you what we need to be able to help you further. We cannot debug files, we don't see.)