Multiselect Sony MXF clips source settings only change the clip which you right click.
When you select multiple Sony MXF clips and change the source setting to S-log from rec 709 only the clip which you right click will change its source settings, all the other will stay at rec 709, seems like a bug to me.
Andrew Jones commented
Just tried with Adobe Support, as it stands they can offer no solution and had no information on when this is coming as an update. It's fine, I didn't have any plans this evening anyway *right clicks 300 clips individually whilst crying into the keyboard*
Sergio Miranda commented
YES same here - not sure why but Sony MXF keeps reverting back to Rec709 in Media Encoder no matter if I disable master effect and change source setting in Premiere pro