The DWDS lists „überarbeiten“ as untrennbar, and all examples given confirm this. But it provides two different pronunciation recordings, one stressed überárbeiten and another stressed úberarbeiten. So I guess there is also a trennbar variant? How often and in what cases would you use it?
#Überarbeiten
brave fjord
wicked forge
The DWDS lists „überarbeiten“ as untrennbar, and all examples given confirm this...
To my mind that has something to do with pronunciation in different regions. Surfing through the web didn't give any significant results on trennbar variant.