I noticed yesterday that my server's hard drive had filled up from files generating in moodledata\localcache. There are all of these long folder names like 8e6e6739-70c9-454a-adbe-8f5e323cf4ff and inside are some more folders with similar names and then in side of each of those folders is a single pdf labelled error.pdf. All of the error.pdf documents say "There was an error while generating this page". When I delete the files, more will show up, sometime right away, sometimes after a few minutes.
Not really sure where to go from here. This has been happening since September with a previous version of Moodle (I think it was 3.3). Noticed it after the hard drive filled up! Updating to latest never changed anything. I went into debugging, set it to log errors & checked the php error log but nothing is showing up. Any advice is appreciated.
Environment: Latest Moodle from Nov. 3, Server 2008 R2, IIS7, MySql 5.5, PHP7.0.9