I've been seeing a lot of issues lately regarding ACF and Memcached. I've also seen topics created by other users regarding the same thing (Dreamhost also uses a memcached drop in). On our servers, in order to squeeze the best performance out of ACF, we have to turn off memcached. Do you have any plans to address the issue? Customers have even complained that fields cannot be edited with it enabled.
I'd be more than happy to help in any way I can, provide you debug reports, xdebug stack traces, etc. I just want to make sure people who use this plugin are getting the best performance on our servers.
Here are some similar topics as well: