I've just upgraded a site from EE 2.1 to EE 2.7.1 and got it basically working by upgrading the associated AddOns. Playa is still having trouble (migrated from 3.1 to the latest 4.4.5).
Simple Playa code that should return the entry_ids for the items selected within the
page_sidebar_content field are instead returning a text string.
is returning something like:
instead of something like