Export troubles - flashing green frames?

Still relatively new to Premiere Pro so hoping this is an easy fix!
After exporting, stock footage that I've downloaded along with transitions flashes with green frames as bellow.

As far as I'm aware I haven't changed any export settings, so I've tried uninstalling and reinstalling both the current version and older versions to no avail.

Also including a screen cap of export setting used in case there is an issue there.

Any help or advice would be greatly appreciated!
Cheers,
Nate