all my edit button cannot work and got "Invalid form POST data" AJAX error
An AJAX HTTP error occurred is very general error and it can be related to many things.

Based on your provided information we can say it's a core callback (/system/ajax) and the callback exists (Result code: 200).

The main problem is that it returns the empty response. This is most likely caused by WSOD (white screen of death) which can be related to:


out of memory issue (increase memory_limit in your php.ini),
timeout issue (increase max_execution_time in your php.ini),
code issue (make sure you don't have any exit() or die() which terminates your code),
cache issue (so please clear your cache, including memcached/redit if you're using it).


To debug this, you should:


Check your watchdog table for any errors (e.g. drush ws --tail --full).
Check your PHP error log for any PHP errors.
Use XDebug PHP extension, after configuring it enable xdebug.auto_trace parameter (only temporary), then reproduce the problem and check the trace file for more details.