Hi, @Chefty, there are three non-printing bytes at the start of the _headers file causing it not to be proceesed:
$ hexdump -C _headers
00000000 ef bb bf 2f 2a 0a 20 20 58 2d 46 72 61 6d 65 2d |.../*. X-Frame-|
00000010 4f 70 74 69 6f 6e 73 3a 20 44 45 4e 59 0a 20 20 |Options: DENY. |
00000020 58 2d 58 53 53 2d 50 72 6f 74 65 63 74 69 6f 6e |X-XSS-Protection|
00000030 3a 20 31 3b 20 6d 6f 64 65 3d 62 6c 6f 63 6b 0a |: 1; mode=block.|
00000040 20 20 52 65 66 65 72 72 65 72 2d 50 6f 6c 69 63 | Referrer-Polic|
00000050 79 3a 20 6e 6f 2d 72 65 66 65 72 72 65 72 0a 20 |y: no-referrer. |
00000060 20 58 2d 43 6f 6e 74 65 6e 74 2d 54 79 70 65 2d | X-Content-Type-|
00000070 4f 70 74 69 6f 6e 73 3a 20 6e 6f 73 6e 69 66 66 |Options: nosniff|
00000080
It is the first three bytes (ef bb bf) causing this issue. If you delete those three bytes from this file, the headers will begin working.
Yes, I spend time doing binary (or hexadecimal in this case) analysis of text files. Why would I do such a thing? Because I’ve seen this root cause before. 