SharePoint Customised form ignoring display settings

Hi, 

I have multiple SharePoint lists where the form has been customised using PowerApps (via the integrate option on the menu bar at the top of the list).  I have set the display setting of the form to be Landscape and Large as I have many fields on the forms. 

However since yesterday when a user adds a new item to the list the forms is now presenting in the centre of the screen and a horizontal scroll bar to access the fields on the right. Previously this was pinned to right hand side of the screen and showed all fields as designed in PowerApps.

I have created a test list again this morning to ensure that I wasn't going mad and this is the result:

This issue has now squished all my existing forms and there are many of them

To recreate this please just create a basic list, customise the form using PowerApps and set the display setting to Landscape / Large.