Hy,
i do encounter a problem while adding or editing articles from frontend in K2 if there is a long text. (small texts work fine !)
The guy from template says that it is a server issue: max_input_vars is too low, that i should increase it up to 25000 vars, that 10000 is not enough. The guy from server company answers that 10000 is far enough, that the problem is in the coding of the component/module/plugin: not all data should be sent in one go !

Anyone an idea how to get this solved?

PHP version 5.6.30-0+deb8u1
MySQL version 5.5.5-10.0.30-MariaDB-0+deb8u2
Upload limit 2M
Memory limit 128M
K2 v2.7.1

What is the actual error message that you are getting?

Hy ,
sorry for this lapsus ...

The error message given is Error 403 forbidden (but only comes after a certain length of text. Short text lengths work fine

Best regards
Thomas

Are you using multiple extrafields with longtext ?

hy,

no extrafields at all ... only the main text field

br
Thomas

hy,
upgraded today to latest joomla version and K2 version.
Error persists :-(

Please advise as the site as is is unusable for our purpose if editors cannot use frontend editing.

Best regards
Thomas

Are you using any 3rd party K2 extensions?
Can you send me an example of an item?

Hy,
how to send you logindata ?

We do not normally look into user's sites.
But you can use our contact form www.joomlaworks.net/support/contact

Changing the extension is not something that we will do, but do check for any 3rd party K2 extensions.