New ticket induces Error 500

Hello,

I initially appended my message at the end of http://www.osticket.com/forum/discussion/87292/open-a-new-ticket-always-returns-500-internal-server-error-invalid-csrf-token-on-ticket-response before I notice it was an old thread with less chance to be viewed. So, I open this new one.

Well, I'm with osTicket 1.9.14 (entire system info at bottom).

Just after a ticket submission, my customers (and my test shows the same
thing) obtain an error 500 about
http://<my-domain>/support/open.php.

Here is the exact message (just masked my domain name):
The <my_domain> page isn’t working.

Nothing in osTicket's System log visible from http://<my_domain>/support/scp/logs.php.

Here is what I see in http://<my_domain>/support/error_log:
[01-Mar-2017
06:32:10 America/Montreal] PHP Fatal error:  Uncaught exception
'Exception' with message 'No such backend registered' in
/home/biiip/public_html/sfy/support/include/class.file.php:693
Stack trace:
#0 /home/biiip/public_html/sfy/support/include/class.file.php(111): FileStorageBackend::getInstance(Object(AttachmentFile))
#1 /home/biiip/public_html/sfy/support/include/class.file.php(115): AttachmentFile->open()
#2 /home/biiip/public_html/sfy/support/include/class.file.php(133): AttachmentFile->sendData(false)
#3 /home/biiip/public_html/sfy/support/include/class.mailer.php(373): AttachmentFile->getData()
#4 [internal function]: Mailer->{closure}(Array)
#5
/home/biiip/public_html/sfy/support/include/class.mailer.php(379):
preg_replace_callback('/cid:([\\w.-]{32...', Object(Closure), '<div
style="dis...')
#6
/home/biiip/public_html/sfy/support/include/class.email.php(168):
Mailer->send('admin.alerts@sh...', 'New Ticket Aler...',
'<h2>Hi Admin,</...', Array)
#7
/home/biiip/public_html/sfy/support/include/class.email.php(178):
Email->sen in
/home/biiip/public_html/sfy/support/include/class.file.php on line 693

And here is the access log for the domain just before the error:
78.218.191.79
- - [01/Mar/2017:06:29:52 -0500] "GET /support/ajax.php/config/client
HTTP/1.1" 200 69 "http://<my_domain>/support/open.php"
"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like
Gecko) Chrome/56.0.2924.87 Safari/537.36"
78.218.191.79 - -
[01/Mar/2017:06:29:53 -0500] "GET
/support/ajax.php/draft/ticket.client.9b41d9ff842e HTTP/1.1" 205 33
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:29:53 -0500] "POST
/support/ajax.php/draft/ticket.client.9b41d9ff842e HTTP/1.1" 200 17
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:30:03 -0500] "POST
/support/ajax.php/draft/2119 HTTP/1.1" 200 2
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:30:47 -0500] "GET
/support/ajax.php/form/help-topic/10 HTTP/1.1" 200 26
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:13 -0500] "POST
/support/ajax.php/draft/2119 HTTP/1.1" 200 2
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:23 -0500] "POST
/support/ajax.php/draft/2119 HTTP/1.1" 200 2
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:33 -0500] "POST
/support/ajax.php/draft/2119 HTTP/1.1" 200 2
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:43 -0500] "POST
/support/ajax.php/draft/2119 HTTP/1.1" 200 2
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:44 -0500] "POST
/support/open.php HTTP/1.1" 200 16318
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:45 -0500] "GET
/support/ajax.php/draft/ticket.client.9b41d9ff842e HTTP/1.1" 205 33
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:45 -0500] "POST
/support/ajax.php/draft/ticket.client.9b41d9ff842e HTTP/1.1" 200 17
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:31:55 -0500] "POST
/support/ajax.php/draft/2120 HTTP/1.1" 200 2
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"
78.218.191.79 - - [01/Mar/2017:06:32:03 -0500] "POST
/support/open.php HTTP/1.1" 500 -
"http://<my_domain>/support/open.php" "Mozilla/5.0 (Windows NT
6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87
Safari/537.36"

The ticket is well submitted, but because of this
error, we (customers) think it's not. So, some give up and some insist
doing I have a lot of duplicate tickets...

Do you have an idea of the reason why ?

--
Server Information
osTicket Version     v1.9.14 (8b927a0)
Upgrade — v1.9.15 is available
Web Server Software     Apache/2.4.25 (Unix) OpenSSL/1.0.1e-fips mod_bwlimited/1.4
MySQL Version     5.5.54
PHP Version     5.6.30
PHP Extensions
gdlib     Used for image manipulation and PDF printing
imap     Used for email fetching
xml     XML API
xml-dom     Used for HTML email processing
json     Improves performance creating and processing JSON
mbstring     Highly recommended for non western european language content
phar     Highly recommended for plugins and language packs
fileinfo     Used to detect file types for uploads
PHP Settings
cgi.fix_pathinfo     "1" is recommended if AJAX is not working
date.timezone     America/Montreal
Database Information and Usage
Schema     biiip_sfyost (localhost)
Schema Signature     b26f29a6bb5dbb3510b057632182d138
Space Used     257.15 MiB
Space for Attachments     243.19 MiB
Installed Language Packs
français, langue française (French) — fr_FR   Verified
Version: 145919, Built: Mon, 28 Mar 16 20:25:30 +0000