Hi Xavier thanks for the response!
Yes, midi thru is enabled in mix>global and it seems that the din5 out is working ok.
As you have suggested, I have sent midi via USB to the preenfm3 and the problem is the same - midi thru to 0-coast via din5 and it is working fine, but midi thru to the nymphes and keystep pro both via din5 is not working properly.
I have now also tried midi din5 out from scarlet 8i6 into preenfm3 and then thru to the keystep pro and that is also not working properly - but the other way - midi din5 out from keystep pro into preenfm3 and then through to scarlet 8i6 is ok - so it very confusing for me!
it seems to be an unusual problem so if there is no solution then I can workaround with a midi through box if required but would prefer not to purchase one if possible.
I also have the v0.109 firmware (it is a relatively new prebuilt purchase from vandaal).
Thankyou in advance for your help!