Can't add and save a custom field

[mySITE4u]

Hello!

I have more than 10 custom fields added for a product and I try to add one more custom(Parent) field, it adds a parent field, which contains two other fields - image and string.
I fill out the fields values, then press Save and...it redirects me to the VM dashboard, no added custom fields saved for the product.

What is the issue, are there any restrictions to custom fields count?

Thanks for advance!