SOLVED!!
On my own!
This was an issue related to a cron job running literally every minute, and creating files in the home directory every time it ran.
I suppose that there is a limit to the number of files that show up in the directory listing.
The directories were indeed still there just not showing in an FTP listing, but in advanced file manager they were.
Solution was just to delete the excess files in the /home/user name/ folder!