Meta Fields => Save loads infinitely

Hello,

I have problem with the “Meta Fields”. It is the Metafield “fpd_products” for the Fancy Product Designer Plugin. I found something in the forum here regarding Wordfence, but I don’t use this plugin.

I’ve testet 2 different Browsers. I tried to deactivate WpRocket and the problem still exists.

“Get Meta fields” works without problem.
When I check the Meta Field and press Save, it loads infinitely. It is simply not saved. What is the reason for this?

As soon as I press “Save” an error is logged in the console (see picture) .

System status
memory_limit : 2048M
max_input_vars : 3000
max_execution_time : 360s

best regards