Adding a QListWidget messes up entire layout

I have a QListWidget inside a layout, and I have that ListWidget/Layout inside my main layout, and whenever i do ListWidget.Show the entire main layout get's messed up. It looks like it get's a bigger spacing or something, however I can't find out why it would do that. Anyone seen anything like it before?

Before ListWidget added:
Attachment 12497

After ListWidget added:
Attachment 12498


Code example if how listwidget is added (This is PyQt 5.8.2 in python 3.6)

First it's added thru the UI-Designer

Code:

---

self.playlist_List = QtWidgets.QListWidget(Form)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.playlist_List.sizePolicy().hasHeightForWidth())
        self.playlist_List.setSizePolicy(sizePolicy)
        self.playlist_List.setFocusPolicy(QtCore.Qt.ClickFocus)
        self.playlist_List.setEditTriggers(QtWidgets.QAbstractItemView.NoEditTriggers)
        self.playlist_List.setObjectName("playlist_List")
        self.playlist_Layout.addWidget(self.playlist_List, 0, 0, 1, 1)

---

Then I create a new Layout, name it bottomLayout and adds that widget to it.

Code:

---

self.bottomLayout = QVBoxLayout()
        self.bottomLayout.setContentsMargins(0, 0, 0, 0)
        self.bottomLayout.setSpacing(6)
 
        self.bottomLayout.addLayout(self.playlist_Layout)

---

Note: This is the layout that gets added to bottomLayout

Code:

---

self.playlist_Layout = QtWidgets.QGridLayout()
        self.playlist_Layout.setSizeConstraint(QtWidgets.QLayout.SetDefaultConstraint)
        self.playlist_Layout.setContentsMargins(6, -1, 6, -1)
        self.playlist_Layout.setSpacing(0)

---