Images ignoring Cache-Control in .htaccess - apache

Question

In my images folder, I have an .htaccess file with the following:
<IfModule mod_headers.c>
# Browsers may cache images for 24 hours, including disk cache for SSL
Header set Cache-Control "max-age=2628000, public, must-revalidate"
</IfModule>
When I curl an image in that folder, I get the following (Notice Cache-Control missing "public" and "must-revalidate"):
HTTP/1.1 200 OK
Server: nginx/1.11.8
Date: Fri, 14 Dec 2018 17:57:00 GMT
Content-Type: image/jpeg
Content-Length: 46563
Last-Modified: Fri, 29 Sep 2017 03:16:20 GMT
Connection: keep-alive
ETag: "59cdbb04-b5e3"
Expires: Fri, 21 Dec 2018 17:57:00 GMT
Cache-Control: max-age=604800
Strict-Transport-Security: max-age=31536000
Accept-Ranges: bytes
It does not matter what I put in the .htaccess file, I always get the above response.
If I create a new image in that folder, I also get the same above response.
If I change the extension on an image in that folder (.bak) I get the expected response (Cache-Control is correct):
HTTP/1.1 200 OK
Server: nginx/1.11.8
Date: Fri, 14 Dec 2018 17:59:35 GMT
Content-Type: image/gif
Content-Length: 19164
Connection: keep-alive
Last-Modified: Fri, 14 Dec 2018 16:07:12 GMT
ETag: "183ca-4adc-57cfd9fbbac00"
Accept-Ranges: bytes
Cache-Control: max-age=2628000, public, must-revalidate
Strict-Transport-Security: max-age=31536000
Any ideas what is going on here? I looked at all parent .htaccess files and apache config, I can not find anything!
Please help!!!

Answer 1

For anyone else experiencing this issue, the Apache .htaccess directive was being overridden by the following Nginx config:
location ~* ^(.+?)(?:\.\d+)?\.(jpe?g|gif|png|svg|ico|bmp|js|css|ttf|eot|woff2?)$ {
root /var/www;
try_files $1.$2 #apache;
expires 7d;
}
Replacing "expires 7d;" with the following did the trick:
add_header Cache-Control "max-age=2628000, public, must-revalidate";