Can't upload files unless I comment out htaccess entries - .htaccess

Question

I have a site that is built on concrete5 (not by me). Now, I added a few lines to the htaccess to add the trailing slash after my urls as the site was loading over both versions.
However, now I cannot upload files to the site. I am just getting errors. There is also an option for users to upload a photo and they get an error too.
The only work around I have is that I can go into htaccess and comment out the lines I added, save it and then upload and the remove the #'s. Whilst this lets me upload in the short term, it's not a viable solution as regular users cannot do this.
My .htaccess is the following:
# -- concrete5 urls start --
RewriteEngine On
<IfModule mod_rewrite.c>
RewriteBase /
RewriteCond %{REQUEST_URI} !(.*)/$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !index.php
RewriteRule ^(.*)$ /$1/ [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>
# -- concrete5 urls end --
I comment out these lines for it to let me upload:
# -- concrete5 urls start --
RewriteEngine On
<IfModule mod_rewrite.c>
RewriteBase /
#RewriteCond %{REQUEST_URI} !(.*)/$
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteCond %{REQUEST_URI} !index.php
#RewriteRule ^(.*)$ /$1/ [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>
# -- concrete5 urls end --
Whilst it looks like that i can upload but lose the trailing slashes so the urls are all messed up.
Anyone know what is going on? FYI I am not a developer but can understand to a degree.

Answer 1

Have you updated all your internal links (and form submission URLs) to include the trailing slash?
My guess is that you are submitting the form to a URL that does not include the trailing slash. The 301 redirect that follows will lose any submitted POST data (as the request is converted to GET).
You need to make sure that you are submitting your form to the canonical URL.