This issue might be caused due to a low value at the max_input_vars parameter.
To fix this problem, go to PHP settings (either php.ini directly or some GUI) and change the max_input_vars parameter(3000-3500 is probably a good range to start with). Learn how to do it.
*What is PHP max input vars?
The PHP Max Input Vars is the maximum number of variables your server can use for a single function.
Optional – feel free to check out our CSV extension if your use case requires creating many different content versions.
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