Container in Item tab under Parcels is wider than screen size

The container in the Items tab under Parcels is wider than the tab it is under. This happens for the container of the list of items and the container of the Add an Item form (see screenshots).

The problem occurs between screen sizes around 975px to 1080px and between screen sizes around 750px to 860px.

The issue appears under Windows 10 with Mozilla Firefox Quantum 68.7.0.