Hi Andy, tagging you here. For about the last week, several of us on the banner team, including @Pcoombe, @jrobell & @TSkaff, have noticed much longer save times on banners - sometimes 15 or even 30 seconds, when it used to be more like 5. This happens when creating a new banner or saving edits to an existing banner.
Timing seems coincidental with the solution to T144952, but might not be related. Thanks!