The 'Auto Features' function was used to install worktops and a similar shape as shown in the example below appears in a 'Perspective' render. This will not show when viewing in a 'Plan' or 'Elevation' mode.
The reason this unusual shape appears and is only visible within a 'Perspective' render is because the 'Auto Joint' function was not selected during the process of adding the worktop.
The Auto Joint button will appear within the steps taken during the inserting and manipulation of the worktops.
This can be remedied by clicking on the Insert tab, then expanding the Auto Features menu and selecting Edit Worktops followed by clicking Next Stage and Auto Joint.