Language override not working on some strings.

I'm using latest FC master version (downloaded today) on joomla 3.5.1
I have also installed Italian language pack, and set Italian lang as default site lang.
Some strings are not translated, also being those strings correctly translated in ini file (and/or added to the IT ovveride ini).
I'm experiencig this in default category view (the COLUMNS button string is not translated in italian) and in flexipagebreak plugin ("Previous page/Next page" strings are not translated).
Waiting for you kindly reply
Regards

ps: I also see that when loading the flexi article with page breaks, the page counter says "1 /11", but after hitting the next page it changes to "1/10", remaining in this state after any forward-backward hitting. Only reloading the page I get 1/11 again.

for previous next page it's in field configuration
for column you what is your string ?
you can participate to italian translation in transifex

I'm aware of that, but I have asked for a different think: I have added the corresponding translated strings to the IT Override ini file (both admin and frontend one), but it still doesn't translate them: is there an issue in php code, or is my fault?

but what is the string that you can't translate ? (string not value)

The text COLUMNS in default category view button....

<input type="button" value="Columns" onclick="fc_toggle_box_via_btn('mainChooseColBox', this, 'btn-primary');" class="btn btn-primary" id="fc_mainChooseColBox_btn">

<span class="label">Columns</span>
<input type="checkbox" align="right" onclick="toggle_column('mainChooseColBox', 'adminListTableFCcategory', 0, 0);" checked="checked" data-colno="0" name="columnchoose_adminListTableFCcategory[0]" id="columnchoose_adminListTableFCcategory_0">

no i want to see you string override ...
like FLEXI_COLUMNS or other