htaccess adding ending slash to some images and not others - .htaccess

Question

New to htaccess... All files exist despite 404. There are actual 50+ images in this one folder but 3 images are getting a slash added to the end.
not working:
http://shawnrieger.dev/img/photography/small/20100402153906_s.jpg/
http://shawnrieger.dev/img/photography/small/20140404123054_s.jpg/
http://shawnrieger.dev/img/photography/small/20130330110114_s.jpg/
an example of working:
http://shawnrieger.dev/img/photography/small/20160913190428_s.jpg
http://shawnrieger.dev/img/photography/small/20120613091849_s.jpg
http://shawnrieger.dev/img/photography/small/20120713102800_s.jpg
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^privacy-policy/$ /parts/pages/privacy-policy.php
RewriteRule ^project/([^/]+)/$ /parts/pages/project.php?id=$1
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/)$
RewriteRule (.*)$ /$1/ [R=301,L]
<IfModule mod_headers.c>
# WEEK
<FilesMatch "\.(jpg|jpeg|png|gif|swf)$">
Header set Cache-Control "max-age=2592000"
</FilesMatch>
# WEEK
<FilesMatch "\.(js|css|swf)$">
Header set Cache-Control "max-age=2592000"
</FilesMatch>
</IfModule>

Answer 1

You must avoid adding trailing slash for real files and also reorder your rules.
Have it like this:
<IfModule mod_headers.c>
# WEEK
<FilesMatch "\.(jpg|jpeg|png|gif|swf)$">
Header set Cache-Control "max-age=2592000"
</FilesMatch>
# WEEK
<FilesMatch "\.(js|css|swf)$">
Header set Cache-Control "max-age=2592000"
</FilesMatch>
</IfModule>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule [^/]$ %{REQUEST_URI}/ [L,R=301,NE]
RewriteRule ^privacy-policy/$ /parts/pages/privacy-policy.php [L,NC]
RewriteRule ^project/([^/]+)/$ /parts/pages/project.php?id=$1 [L,NC,QSA]
Make suer to clear your browser cache before you test this change.