Strange behavior forcing to use a slash in the URL for my API Swagger documentation

I have a NodeJS app running on port 9115. This is the app where I keep all my APIs, and the beginning of each call is like this: https://example.com/api/. For example: https://example.com/api/users/:id.

I use Swagger to document my APIs and I implemented it as explained here: https://dev.to/kabartolo/how-to-document-an-express-api-with-swagger-ui-and-jsdoc-50do

When I go to https://example.com/api/docs/, everything is fine I have the correct swagger page, but if I don't put the last slash (https://example.com/api/docs), I get a 404. Actually, I get a 404 and the URL shown in my address bar is https://example.com/docs, which I don't understand.

Here is my Apache config:

<VirtualHost *:80>
ServerAdmin admin@example.com
ServerName example.com

RewriteEngine on
RewriteRule ^(.*)$ https://example.com$1 [R=302,L]

<Location /api>
  ProxyPass http://127.0.0.1:9115
  ProxyPassReverse http://127.0.0.1:9115
</Location>

ErrorLog /var/log/site.local-err.log
CustomLog /var/log/site.local-acc.log combined
</VirtualHost>

<VirtualHost *:443>
  ServerAdmin admin@example.com
  ServerName example.com
  SSLEngine On
  SSLCertificateFile /etc/ssl/certs/site.com.pem
  SSLCertificateKeyFile /etc/ssl/private/site.com.key

  ErrorLog ${APACHE_LOG_DIR}/site.local_https-error.log
  CustomLog ${APACHE_LOG_DIR}/site.local_https-access.log combined

  SSLProxyEngine On
  ProxyPreserveHost On

   <Location /api>
    ProxyPass http://127.0.0.1:9115
    ProxyPassReverse http://127.0.0.1:9115
   </Location>

</VirtualHost>

When I look at the log, I see that when I put https://example.com/api/docs the log shows "GET /docs/ HTTP/1.1" 404 and when I put https://example.com/api/docs/ the log shows "GET /api/docs/ HTTP/1.1".

Could anybody explain me what I'm doing wrong here? I checked other StackOverflow answers but they concerned PHP and parameter rewriting.