Advanced Custom Fields is a really useful plugin. However, it can conflict with one main performance enhancing feature - WordPress' Object Cache. They can't be used together, we'll explain why in this article...
The Advanced Custom Fields plugin disables persistent caching, as shown in the following function on line 30...
While using an Object Cache boosts performance for your site, using this plugin with it enabled can cause inconsistencies and unexpected behavior. See more information about this issue here.
If not using the plugin isn't an option you can attempt to use the redis-cache plugin workaround. Feel free to Contact support if you require additional assistance, or have further questions about this.