Latest one was released on the 3rd of December 2019 - M32.R.0527 .For the Sony player i don't see any other firmware updates bot to mention that is a 2016 product. The last one came out a year ago? And it was just to remove some outdated services like Gracenote. Basically check your TV for updates and your AV receiver (if it has this feature).
Unfortunately the TV and AVR doesn't have any latest update for now.
As you've mentioned, it could be any of the settings on the player. (have tried almost all but still at a lost)
The worse part is, it only occurs ONCE...and then for the remaining time of the movie, everything is fine.
I called up SONY but they just told me to get it to the service center to get it fixed