I have the same / or a very similar problem: I have a 9 fields with 10 nested repeaters each, all showing up on a page. The fields started saving ok, but after a while wp-admin would start to come up with issues. I have been able to fend these off with define(‘WP_MAX_MEMORY_LIMIT’, ‘-1’); , and the following php.ini entries:
mysql.connect_timeout = 120
expose_php = Off
max_input_time = 42000
allow_url_fopen=1
max_execution_time = 42000
memory_limit = 256M
max_file_uploads = 256M
file_uploads = On
post_max_size = 256M
upload_max_filesize = 256M
max_input_vars = 50000
max_input_nesting_level = 256
However, there page now seems to have reached another ceiling and no matter what I do, it won’t save changes. It times out after 2 mins and goes to a 404 page(/wp-admin/post.php). MySQL has surprisingly appears to have 282359 wp_postmeta entries, which I thought was quite a lot, and the ACF seems to have stopped saving rows half the way through its last save.
Any clues as to what might be causing this limit? Is it a timeout issue? There doesn’t seem to be a problem with the field character size as it’s not that long.
Could anyone think of a reason?