Ornatrix (3ds Max) to UE5 - Alembic import problem

I’ve started working on the hair system. I’m using the Ornatrix plugin of 3ds Max to create the groom, and exporting it as an Alembic file into UE5. Yesterday I did the eyebrows and they look okay (for now I’m concentrating on the technical process rather than a convincing groom) but I’ve run into problems with the eyelashes. In fact, I think I had the same problem with the eyebrow, but it’s not as obvious because there are so many individual hairs. In the case of the eyelashes – with only a handful of hairs – the problem becomes very apparent.

the eyebrow groom in 3ds Max (bottom) and in UE5 (top)

The problem is apparent in the eyelashes. Only a fraction of the hairs are being imported into UE5. I spent a few hours tearing my own hairs out trying to figure out where the problem lay. In the screenshot below, I’ve exported the .abc file as usual and then immediately re-imported it back into Max as a V-Ray proxy object. It’s clear that all of the hairs are accounted for.

the Ornatrix groom in black and the V-Ray proxy in yellow – all the hairs are present in the V-Ray proxy

And just to really make sure that the problem was not in the Ornatrix groom or export process, I installed Blender and imported the very same .abc file there.

the hairs in Blender compared to a screenshot from V-Ray (inset) showing that all the hairs are accounted for in the exported .abc file – the red lines have been added for a direct comparison of the number of hairs

And then when I import to UE5, I get a fraction of the hairs. The highlighted area in the corner tells me that there are four curves in total (one is on the other eye) and sixteen guides. There should be twenty curves in total, so maybe UE5 is converting some to guides. I have utterly no idea why this would happen. I’ve never used the Alembic format before today so I’m really in the dark. The majority of the documentation for Ornatrix is written for the Maya implementation – though it seems that I’ve isolated the problem to the UE5 import process so this shouldn’t present a big problem. So far, the UE5 documentation that I’ve come across is super technical and I don’t understand it - or it refers to the UE4 Alembic import process.

Three hairs visible in UE5, compared to eleven in the original groom, the V-Ray proxy and the Blender import

So if anyone has any ideas, I'm all ears!