Clockpicker if position fixed doesn't show up at first click

Question

I have a problem that I am not finding a solution.

I decided to put clockpicker in position fixed:

.popover.clockpicker-popover{
    position:fixed;
    padding-top:80px;
}

With this setting, I dont't know why, I have to click 2 time on my input to make clockpicker visibile. I know that there could be problem with z-index but it seems like if I change the z-index from the console of the input-wrap in the first try works but then it stops and the previous behaviour come back. This is my input field:

<div class=" select  eff01 col-50" style="position:relative">
<label>*Orario</label>
 <div class="input-wrap" style="border: 1px solid rgb(187, 187, 187);">
    <input class="form-control required time" id="TrainManuallyDepartureTime" autocomplete="off" readonly="readonly" type="text">                        
    </div>
    </div>

Do you have any suggestions?