jquery-UI: Draggable div only drags vertically, not horizontally

I'm trying to have my draggable area constrained to the background (.bg), but once I do that the window is only draggable vertically, despite the background having a width of 100%.

I tried the same with putting the constraint to "body" as well as "parent", all resulting in the same issues.

How would I be able to make my window draggable in all directions?

$( function() {
    $( ".draggable" ).draggable({
        handle: ".window-titlebar",
        scroll: false,
        containment: ".bg"
    });
  } );

/* - - - GENERAL - - - */
body,html {
    font-family: Roboto;
    font-size: 18px;
    height: 100%;
    width: 100%;
    margin: 0;
}

.bg { 
  background-image: url("http://abload.de/img/background4mqdx.jpg");
  height: 100%;
  width: 100%;
  background-size: cover;
  background-repeat: no-repeat;
}
/* - - - WINDOWS - - - */

.window {
    display: flex;
    flex-direction: column;
    
    min-width: 30%;
    width: fit-content;
    padding: 4px 5px 5px 4px;
    height: 70%;
    box-shadow: -1px -1px 0px 0px #000 inset, 1px 1px 0px 0px #FFF inset, -2px -2px 0px 0px #868A8E inset;
    background-color: #C2C5CA;
    margin: 0 auto;
}
.window-titlebar {
    display: block;
    background: linear-gradient(to right, #000080, #0992ec);
    position: relative;
    width: 100%;
    height: 25px;
    color: #FFF;
}
.window-titlebar > .tab-icon {
    margin-right: 5px;
}
.window-option-bar {
    display: block;
    position: relative;
    width: 100%;
    height: 18px;
    padding: 5px 0px 8px 0px;
}
.window-option {
    -webkit-user-select: none;
    padding: 2px 5px 2px 5px;
    cursor: pointer;
}
.window-option:hover {
    box-shadow: 2px 2px 0px 0px #000 inset, -1px -1px 0px 0px #FFF inset;
}
.window-content {
    margin-left: auto;
    margin-right: auto;
    display: block;
    width: calc(98.5% - 7px);
    height: 100%;
    border: 2px solid #C2C5CA;
    box-shadow: -1px -1px 0px 0px #000, 1px 1px 0px 0px #FFF;
    background-color: #FFF; 
    overflow: scroll;
    padding: 5px;
}

    <!-- JavaScript -->
    <script src="https://code.jquery.com/jquery-3.1.0.min.js"></script>
    <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
  
<body>
  <div class="bg">
    <!-- Windows -->
     
    <div class="window menu-context draggable" id="credits-window" >
        <div class="window-titlebar">
            <div class="tab-icon"></div> credits - Notepad 
        </div>
        <div class="window-option-bar">
        </div>
        <div class="window-content">
             hewwo
        </div>  
    </div>
  
  </div>
 </body>

Solution

I asume this question was solved already, but just in case.
Just add the css property position with the value absoulte to the .window class, and it should work.

$( function() {
    $( ".draggable" ).draggable({
        handle: ".window-titlebar",
        scroll: false,
        containment: ".bg"
    });
  } );

/* - - - GENERAL - - - */
body,html {
    font-family: Roboto;
    font-size: 18px;
    height: 100%;
    width: 100%;
    margin: 0;
}

.bg { 
  background-image: url("http://abload.de/img/background4mqdx.jpg");
  height: 100%;
  width: 100%;
  background-size: cover;
  background-repeat: no-repeat;
}
/* - - - WINDOWS - - - */

.window {
    position:absolute;
    display: flex;
    flex-direction: column;
    
    min-width: 30%;
    width: fit-content;
    padding: 4px 5px 5px 4px;
    height: 70%;
    box-shadow: -1px -1px 0px 0px #000 inset, 1px 1px 0px 0px #FFF inset, -2px -2px 0px 0px #868A8E inset;
    background-color: #C2C5CA;
    margin: 0 auto;
}
.window-titlebar {
    display: block;
    background: linear-gradient(to right, #000080, #0992ec);
    position: relative;
    width: 100%;
    height: 25px;
    color: #FFF;
}
.window-titlebar > .tab-icon {
    margin-right: 5px;
}
.window-option-bar {
    display: block;
    position: relative;
    width: 100%;
    height: 18px;
    padding: 5px 0px 8px 0px;
}
.window-option {
    -webkit-user-select: none;
    padding: 2px 5px 2px 5px;
    cursor: pointer;
}
.window-option:hover {
    box-shadow: 2px 2px 0px 0px #000 inset, -1px -1px 0px 0px #FFF inset;
}
.window-content {
    margin-left: auto;
    margin-right: auto;
    display: block;
    width: calc(98.5% - 7px);
    height: 100%;
    border: 2px solid #C2C5CA;
    box-shadow: -1px -1px 0px 0px #000, 1px 1px 0px 0px #FFF;
    background-color: #FFF; 
    overflow: scroll;
    padding: 5px;
}

<!-- JavaScript -->
    <script src="https://code.jquery.com/jquery-3.1.0.min.js"></script>
    <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
  
<body>
  <div class="bg">
    <!-- Windows -->
     
    <div class="window menu-context draggable" id="credits-window" >
        <div class="window-titlebar">
            <div class="tab-icon"></div> credits - Notepad 
        </div>
        <div class="window-option-bar">
        </div>
        <div class="window-content">
             hewwo
        </div>  
    </div>
  
  </div>
 </body>