Caching problem cause language error at first load

[Peter83]

I'm trying to solve a bug with the elgg_set_plugin_setting for "allowed_languages", it suffers of caching problems, continuously deleting and rewriting the plugin setting on the DB, causing also a first load language selection error when the browser language it's different from default one.
I'm debugging with DB table "private_settings" opened to get the point but I'm not able to solve it, it seems that
elgg_register_plugin_hook_handler("all", "plugin", "language_selector_invalidate_setting");
and
elgg_register_event_handler("all", "plugin", "language_selector_invalidate_setting");

are involved in the caching problem, since when commenting this lines the problem disappear.
The language_selector_invalidate_setting is invoked correctly only one time during the hook trigger 'setting','plugin' just before the setPrivateSetting, but the data on the private_settings DB table disappears during the page cycle execution (I guess inside the elgg_trigger_event('init', 'system').
I'm running elgg 1.8.18.
Thank you for help.