Prestashop 1.7.7.3 Backoffice not displaying correctly (narrow)

[inspectaclueso]

Hi,

I've been using PS 1.7.7.3 for a couple of months and all has seemed normal until I logged into back office today and a large number of the backoffice pages are all wonky.  The views are all narrow now?

Dashboard page, shopping carts, products and module manager pages appear normal but most of the others have squished the contact into a narrow band?

Why has this happened and how to fix it?

Thanks

[inspectaclueso]

Turns out a recently installed module (Humm) caused a css conflict.