ERROR: The file could not be written to disk.

Hello!

I am suddenly having an issue on multiple EE 7.5+ sites where, intermittently, random images cannot be uploaded and return the error: “The file could not be written to disk.”

This happens with File and File Grid fieldtypes in the CP Publish Entry form.

I have tried various combinations of disabling XXS filtering both in the CP and through Config Overrides. This does not change anything.

The only possible anomaly I see is when I check PHP Info in the CP, “upload_tmp_dir” says “no value.”

However, running echo sys_get_temp_dir() . PHP_EOL; in an independent .php file returns ‘/tmp ’ as expected.

There has been one instance where the client received the error on attempted upload, but I was able to upload the same file they emailed to me. This was not the case for a different file they had the same issue with.

Set Up:

1. ExpressionEngine 7.5.5

2. PHP 7.2 and 8.2

3. Exif Enabled

4. memory_limit: 768M

5. post_max_size: 512M

6. upload_max_filesize: 256M

I can FTP files to the upload Dir and sync the folders in the CP and that works fine, but kinda clunky. No way I can get one of these clients to do that.

Any help or insights would be much appreciated!