"Your storage is almost full (98%)" but we have 209.1GB available on volume

On the admin web client, we see a message "Your storage is almost full (98%)". The OwnCloud client keeps displaying "Operation canceled" when trying to sync. There is 209.1GB available on Owncloud volume.
I used the Ubunutu software updater which included a couple minor patches to Owncloud. I then rebooted the server. Still receiving the error.

I should point out that I have Owncloud installed on one volume with OS, Apache, mySql, etc and the Owncloud data on another volume. The first volume was low on diskspace. The second volume has 209GB. I'm wondering if this may be part of the problem.

Steps to reproduce
1.Click on files while logged in as Admin with web browser
2.Try to synchronize files using client.
3.

Expected behaviour
It shouldn't report it is out of diskspace.

Actual behaviour
It is saying it's out of diskspace

Server configuration
Operating system: Ubuntu
Web server: Apache
Database: MySQL
PHP version: 7.0.15
ownCloud version (see ownCloud admin page): 9.1
Updated from an older ownCloud or fresh install: updated from 9
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption):
No

ownCloud log (data/owncloud.log)
{"reqId":"zaFf1McSP4HZ5vwg8OTr","remoteAddr":"192.168.2.1","app":"PHP","message":"Uncaught Error: Access to undeclared static property: OC\Files\Filesystem::$normalizedPathCache in \/var\/www\/owncloud\/lib\/private\/Files\/Filesystem.php:772\nStack trace:\n#0 \/var\/www\/owncloud\/lib\/private\/Files\/View.php(2039): OC\Files\Filesystem::normalizePath('\/aevenard\/files...')\n#1 \/var\/www\/owncloud\/lib\/private\/Files\/View.php(1151): OC\Files\View->unlockFile('\/ConnectNGo\/Con...', 1)\n#2 [internal function]: OC\Files\View->OC\Files\{closure}()\n#3 \/var\/www\/owncloud\/3rdparty\/icewind\/streams\/src\/CallbackWrapper.php(109): call_user_func(Object(Closure))\n#4 [internal function]: Icewind\Streams\CallbackWrapper->stream_close()\n#5 {main}\n thrown at \/var\/www\/owncloud\/lib\/private\/Files\/Filesystem.php#772","level":3,"time":"2017-02-26T08:04:01-05:00","method":"GET","url":"\/owncloud\/ocs\/v2.php\/apps\/notifications\/api\/v1\/notifications?format=json","user":"OC_CNG_Admin"}
{"reqId":"7z1f4YZsu+1zw5Glk4dW","remoteAddr":"192.168.2.1","app":"PHP","message":"Uncaught Error: Access to undeclared static property: OC\Files\Filesystem::$normalizedPathCache in \/var\/www\/owncloud\/lib\/private\/Files\/Filesystem.php:772\nStack trace:\n#0 \/var\/www\/owncloud\/lib\/private\/Files\/View.php(2039): OC\Files\Filesystem::normalizePath('\/aevenard\/files...')\n#1 \/var\/www\/owncloud\/lib\/private\/Files\/View.php(1151): OC\Files\View->unlockFile('\/ConnectNGo\/Exe...', 1)\n#2 [internal function]: OC\Files\View->OC\Files\{closure}()\n#3 \/var\/www\/owncloud\/3rdparty\/icewind\/streams\/src\/CallbackWrapper.php(109): call_user_func(Object(Closure))\n#4 [internal function]: Icewind\Streams\CallbackWrapper->stream_close()\n#5 {main}\n thrown at \/var\/www\/owncloud\/lib\/private\/Files\/Filesystem.php#772","level":3,"time":"2017-02-26T08:04:06-05:00","method":"PROPFIND","url":"\/owncloud\/remote.php\/webdav\/","user":"OC_CNG_Admin"}
{"reqId":"3EEFozaLXvB9T0OuNfb1","remoteAddr":"192.168.2.1","app":"PHP","message":"Uncaught Error: Access to undeclared static property: OC\Files\Filesystem::$normalizedPathCache in \/var\/www\/owncloud\/lib\/private\/Files\/Filesystem.php:772\nStack trace:\n#0 \/var\/www\/owncloud\/lib\/private\/Files\/View.php(2039): OC\Files\Filesystem::normalizePath('\/aevenard\/files...')\n#1 \/var\/www\/owncloud\/lib\/private\/Files\/View.php(1151): OC\Files\View->unlockFile('\/ConnectNGo\/Con...', 1)\n#2 [internal function]: OC\Files\View->OC\Files\{closure}()\n#3 \/var\/www\/owncloud\/3rdparty\/icewind\/streams\/src\/CallbackWrapper.php(109): call_user_func(Object(Closure))\n#4 [internal function]: Icewind\Streams\CallbackWrapper->stream_close()\n#5 {main}\n thrown at \/var\/www\/owncloud\/lib\/private\/Files\/Filesystem.php#772","level":3,"time":"2017-02-26T08:04:40-05:00","method":"GET","url":"\/owncloud\/index.php\/core\/preview.png?file=\/ConnectNGo\/Connect+%26+Go\/Archive\/events\/2016\/Ubisoft_Lapins_Cretins\/Website\/Wristband-User+interface\/Design_Desktop\/LapinCretin_Site-V7_10.10-profil_enfant_pop-up_boutique.jpg&c=bd02d0a437d0f9ca6f1937edf55a1072&x=150&y=150","user":"OC_CNG_Admin"}

Integrity status for oC9+
No errors have been found.

Please always provide the full version (e.g. 9.1.1) for your running ownCloud version. An output of:

df -h

from your server might also help.