Magento 2.2 - Cannot update attribute values

Question

I've created some custom product attributes with REST API, correctly populated them and assigned values to products.

Everything works fine in dev environment whereas I got difficulties in staging environment, even though values and settings are the same, even in the DB. If, for example, I want to update the value of "is_filterable" option in an existing attribute from the backend, Magento says it saved the attribute correctly, but actually no changes are made.

I've tried to update with a PUT call to REST API with correct values, but I'm able to update only the attribute labels,

This is the json i'm passing to "products/attributes/my_attr"

    {"attribute":{"attribute_code":"my_attr","attribute_id":174,"scope":"Global","default_frontend_label":"my_attr","frontend_labels":
[{"store_id":1,"label":"my_attr"}],"frontend_input":"select","is_searchable":true,
"is_visible_in_advanced_search":true,"is_comparable":true,"is_filterable":true}}

And this is the Json response, where you can see it is totally ignoring the values for is_filterable and scope.

    {"is_wysiwyg_enabled":false,"is_html_allowed_on_front":false,"used_for_sort_by":
true,"is_filterable":false,"is_filterable_in_search":false,"is_used_in_grid":
true,"is_visible_in_grid":true,"is_filterable_in_grid":true,"position":0,
"apply_to"[], "is_searchable":"0","is_visible_in_advanced_search":"0",
"is_comparable":"0","is_used_for_promo_rules":"0","is_visible_on_front":"0",
"used_in_product_listing":"0","is_visible":true,"scope":"global",
"attribute_id":174,"attribute_code":"taglia","frontend_input":"select",
"entity_type_id":"4","is_required":false,"....

Obviously I've reindexed and cleared caches continuously.

The only way I managed to change those values is directly from the DB. I'm going to try with an extension but I'm not sure to succeed.

I've seen there was an issue that should have been fixed in older Magento versions and actually other attributes work fine.

Any clue?

EDIT: I managed to update values with a REST API request, but still not able to save directly from the backend. This is the updated call (array version)

$data = [
    "attribute" => [
        "attribute_code" => $my_opt,
        "attribute_id" => 173,
        "entity_type_id" => 4,
        "scope" => "global",
        "default_frontend_label" => $my_opt,
        "frontend_labels" =>  [
            ["store_id" => 1,
            "label" => $my_opt ]
        ],
        "frontend_input" => "select",
        "is_wysiwyg_enabled" =>   true,
        "is_html_allowed_on_front" =>  true,
        "used_for_sort_by" =>  true,
        "is_filterable" =>  true,
        "is_filterable_in_search" =>  true,
        "is_used_in_grid" =>  true,
        "is_visible_in_grid" =>  true,
        "is_filterable_in_grid" =>  true,
        "position" =>  1,
        "is_searchable" =>  true,
        "is_visible_in_advanced_search" =>  true,
        "is_comparable" =>  true,
        "is_used_for_promo_rules" =>  true,
        "is_visible_on_front" =>  true,
        "used_in_product_listing" =>  true,
        "is_visible" =>  true
    ]

];

EDIT2: Moreover, if I try to update some info from the backend, Magento resets the values of the default view store label to empty and the "use in layered navigation" to "No". Stranger at any try.

EDIT 3 seems like the most possible issue can be caused by duplicated values in these dropdown attributes, but I carefully removed all of them from

eav_attribute_option
eav_attribute_option_value

in the db, but actually removing options only, works from the backend too, whereas the creation of new options is not working

Answer 1

This is not a definitive solution, for which I will create a new question to which someone hopefully will be able to answer, but I wanted to post at least what the true problem is.

Actually, I observed that everything was working until a certain amount of options, and after that, no matter what the values were, it quit working. Actually I experienced it also in the dev environment, for which the limit was higher, but for an attribute with more than 1300 options, nothing was working as well.

So looking around I found out this is a php memory problem and that you have to increase the value of

max_input_vars=100000

whereas by default is only 1000.

someone suggest also other parameters, but this is actually the most used. The problem that remains, is that I still have not found the good values to have my attributes with many options, to work.