cache error: invalid byte sequence in UTF-8

[amtest]

In normal way the request is coming like this way

    Parameters: {"utf8"=>"✓", "status_id"=>"12686"}

other than, from one client the requst coming like this way

    Parameters: {"utf8"=>"\xE2??", "status_id"=>"12686"}

So this time i am getting this error "ActionView::Template::Error (incompatible character encodings: UTF-8 and ASCII-8BIT)", from client browser, so i am bit confused, where this is happening actually, one place is

    <%= form_for(resource, :as => resource_name, :url => 
    session_path(resource_name), html: { class: "signup" }) do |f| %>

is there any issues with clients browser? in these two statements, what will be the most change to occur this?

will this solution Ruby on Rails "invalid byte sequence in UTF-8" due to bot solve this problem?