Should be fixed in 4.13.2, sorry about that!
Sheer nerd curiosity, if you’re willing to share … what caused this, how’d you resolve it?
Latest Electron let renderer process take an App Nap and be otherwise slowed down in the background 
Disable Chromium's backgroundThrottling on the playback window and hold a
'prevent-app-suspension' powerSaveBlocker while playing or buffering.
