Error at attachment-link

Hello,
when I attach a file to an appointment, it is loaded into the appropriate directory. However, I receive the following error message when called in the frontend - see attachments

I think it is an attitude, but find nothing appropriate.
Does somebody has any idea?

Thank's, Dietmar

Hi, can you describe each step, how you upload a file!
Why do you upload only a part and not the whole pdf?
I can' t reproduce your problem.

Hi, I think there is somewhere the problem - has also always worked.
The procedure is the following:
- I choose the event
- then I select attachments - select file
- Access level: Public
- I forgive the file names
- and click save

Then I get the following message: The entry has been saved

The files appear in the frontend, but when I click on the link, I get this message - but only in Firefox.
The other browsers show a file with 0 bytes.

I've tried the same again on a test server (this is a 1: 1 copy of the live server). Here I don't have the problem ????

Which Joomla Version do you use?
Which PHP Version?
Which JEM Version?
Do you use JEM-Responsive overrides?

Eventually it helps us if you give a url to your site?

On both servers:
- Joomla 3.8.12
- PHP: 7.1.21
- JEM: 2.2.3
- Overrides: 1, for COM_JEM_EVENT_CUSTOM_FIELD1 -> a new text

Where do you store the attachment of an event?
Go to Backend -> JEM -> Settings -> Global Parameteres -> Attachment Folder Path.
It should be: /<joomlaroot>/media/com_jem/attachments and make shure that users have access to this files.
Permissions (unix) at my webspace are 755 for the folders in /attachments/ and 644 for files.