After using GO for a few years without many problems, we suddenly can't download any file anymore. When we try to open or download a file, you see the error:
Could not output file because output has already been sent. Turn off output buffering to find out where output has been started.
There is no error in the php error log. When I go to php.ini, the output_buffer is at 4096. When I turn off the output buffer and restart php, when I download a file I see the entire content of the file in the browser in plaintext (so a bunch of gibbrish if you open a .jpg or .pdf). No error or any content that shouldn't be there on top of it. Just the header is sent as text/html instead of application/pdf or whatever the file is.
I'm running php 5.6 and groupoffice 6.1.130. The only thing I remember doing recently is adding $config['zlib_compress']=true; to the config, since GO was running increadibly slow after recovering a backup of my server. Since the option crashed whole group office, I changed it to "false" so GO would work again. I think that since that moment this problem started happening. Anyone who could point me in the direction of a solution? Thanks!