I would like to check whether the image used for 2017 Q3 6186028 / 32949: BRIGHT YELLOW MINI HEAD NO.728 is correct as it is the same head (just different images) as in 2019 Q4 6265014 / 54117: BRIGHT YELLOW MINI HEAD , NO. 2899 which was recently identified above.
Going through Wadapan's site I believe the following six pieces are the missing ones.
6221031 / 37732: BRIGHT YELLOW MINI HEAD NO. 823
6221034 / 37734: BRIGHT YELLOW MINI HEAD NO. 1029
6016049 / 88584: BLACK MINI LOWER PART 26/199
6254591 / 88585: BLACK MINI UPPER PART NO. 4597
6255037 / 49717: BRICK YELLOW MINI LOWER PART NO. 1655
6255074 / 49718: DARK STONE GREY MINI LOWER PART, NO. 1657
There is a BAM variant on Bricklink of that Torso that doesn't have either arm or back printing. I think that is likely the one.
https://www.bricklink.com/v2/catalog/catalogitem.page?P=973pb3529c01#T=P&C=11
Just been to my local LEGO store today in Southampton and picked up the new figures. The Horseriders Torso and helmet are actually black, along with white/black dual molded legs, not the dark blue they appear in the images above.