Crossposting from Odforce. Had no luck there yet.
I'm really not having an easy time adapting to Solaris...so you might need to explain like I'm five.

I have a RedshiftRendeSettings node that sets up all the usual AOVs, It's writing multiple frames, it's fine.
Above that node I have a renderVars node that sets up the cryptomatte. I tested a bunch of single frames and only when I submitted the big render did I realise that it's only writing to one frame number for that seperate AOV output.

This is the output path on that renderVars node (the @EYE strings are custom pipeline wrangles):
q:/`@EYE_g0_name`/Build/`@EYE_g1_name`/`@EYE_g2_name`/`@EYE_g3_name`/render/3d/`@EYE_element_type`-`@EYE_element_name`_v`padzero(3,@renderversion)`/`@passname`/CRYPTO.$F4.exr

it looks like it's continually overwriting this frame:
CRYPTO.0250.cryptomatte.exr
250 is the end of the frame range in the USD ROP

As I step through the range in solaris, the output path in the scene graph reads correctly for the renderVars and the current frame...so it might be globally overwriting that path as it runs through the time-range for every frame of the USD write.
Greatful of any help!