There are a few issues with the 2016 theme but the fixes are spread out in threads here and on various mailing lists which makes it hard for people moving to the 2016 theme to know where to start/what to prioritise so I thought it might be useful to try to collate them.
The way it works is you can use this thread for general discussion and to post fixes. If you'd like to post a fix please post it and I can add it to a shared document linked from this initial post; there is a template below but if you don't have enough info for the template please go ahead and post a fix regardless as any info will be helpful.
My college is still on the 2012 theme and I'm working on collating the issues myself & will add to the thread as I go but it's going to take a while so I'd like to get the ball rolling. If anyone has any thoughts on how to organise this let me know.
Sample template for posting a known issue:
(if you don't know the info for one of the sections below just put 'unknown')
Issue: [title of issue]
Description: [brief outline of issue]
Article: [BTBB article if known]
Fixed in: [which version of BB fixes this]
Source (if applicable): [link to where the fix was mentioned if possible]
Workaround: [how to fix it; if it's done via custom CSS post the CSS snippet below]
CSS to Resolve Issue (if applicable): [add the CSS here]
Notes: [any other applicable info]