In newer PHP-Versions the count of input-fileds per formula (POST) will be limited to 1000 (unverified information). It seams that this limit is already installed in certain
Apparently it looks like a patch on linux environment causing this issue. If your server has this patch 'suhosin', likely to be the issue. Also its not possible to override this in runtime rather include in your php.ini
suhosin.post.max_array_depth
suhosin.post.max_array_index_length
suhosin.post.max_name_length
suhosin.post.max_totalname_length
suhosin.post.max_vars
suhosin.post.max_value_length