I had one student in a course. When I remove this student and create incremental backups. I get the following error on the moodle client when I update.

Warning: unlink(C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/918cb817dc2eadc041bb79bffd41188f-4847c11ea9f1a/user_files/0/3) [function.unlink]: Permission denied in C:\projects\VLE\Mobile Moodle\environments\xampplite-win32-1.6.6.exe\development\offlinemoodle-0.4\htdocs\moodle\lib\xdelta.class.php on line 219
"C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/xdelta/xdelta3.exe" -d -s "C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/918cb817dc2eadc041bb79bffd41188f-4847c11ea9f1a/moodle.xml" "C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/ef487e3eee20dc3b730930f554b5f5c6/files/moodle.xml.diff" "C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/918cb817dc2eadc041bb79bffd41188f-4847c11ea9f1a/moodle.xml.undiff"

• line 240 of lib\xdelta.class.php: call to debugging()
• line 169 of backup\incremental_backuplib.php: call to xdelta->apply_diff()
• line 245 of backup\incremental_backuplib.php: call to apply_incremental()
• line 69 of backup\get_incremental.php: call to download_incremental()

C:\projects\VLE\Mobile Moodle\environments\xampplite-win32-1.6.6.exe\development\offlinemoodle-0.4\htdocs\moodle\backup>"C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/xdelta/xdelta3.exe" -d -s "C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/918cb817dc2eadc041bb79bffd41188f-4847c11ea9f1a/moodle.xml" "C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/ef487e3eee20dc3b730930f554b5f5c6/files/moodle.xml.diff" "C:/projects/VLE/Mobile Moodle/environments/xampplite-win32-1.6.6.exe/development/offlinemoodle-0.4/moodledata/temp/918cb817dc2eadc041bb79bffd41188f-4847c11ea9f1a/moodle.xml.undiff"
apply diff failed: Dest file tree is different to that expected in diff
Stack trace:

• line 1651 of lib\deprecatedlib.php: call to debugging()
• line 171 of backup\incremental_backuplib.php: call to error()
• line 245 of backup\incremental_backuplib.php: call to apply_incremental()
• line 69 of backup\get_incremental.php: call to download_incremental()

When I add the user back the error goes. I'm pretty sure it's looking for a folder for the user that doesn't exist and is failing as a result.