Decklink Mini Recorder 4k not recognising 1080p 60fps?

I'm hoping somebody can help me get to the bottom of this.

I've just installed a BM mini recorder 4k card (blackmagicdesign[dot]com/uk/products/decklink/techspecs/W-DLK-33) and it's behaving in a way I wasn't expecting.

I am using the card connected to a PTZOptics 30x SDI camera (ptzoptics[dot]com/sdi)

As far as I can tell from the specs the BM Decklink card should accept a variety of resolutions and frame rate combinations but Media Express is telling me the following:

- Camera set to 1080p60 = Media Express detects the signal as 1080p30 but changing the BM Decklink settings to 1080p30 still doesn't produce a picture

- Camera set to 1080p50 = Media Express detects the signal as 1080p25 but changing the BM settings to 1080p25 still doesn't produce a picture

- Camera set to 1080i60 = Media Express detects the signal correctly as 1080i60 and Media Express displays camera feed.

- Camera set to 1080p30 = Media Express detects the signal correctly as 1080p30 and Media Express displays camera feed.

I should add that using an SDI to HDMi converter the BM Decklink recognises and displays 1080p60 flawlessly and it also did in an Elgato capture that I tested for comparison.

I have also tried a variety of other settings for the BM card including 59.94 and 29.97 variants but no joy.

I have tried the most recent firmware for the Decklink card and also rolled back to a previous version (10.4) but no joy either.

Does anybody know what is going on and how I might get the card to recognise the full 1080p60 fps over SDI?

Many thanks!