It's jumper S3. It needs to be installed.
There is a block of 4 jumpers together next to the big Bung IC on the circuit board, s1, s2, s3, s4.
It looks like on a GDSF7 s1-s4 are all not installed. On a PSF2 S3 is installed. I installed S3 on a GDSF7 and now it defaults to English (turned it into a PSF2).