I've noticed a change in how Arnold is applying mapping data from Gradient Ramp shader using Tyflow's Mapping operator. The Max Viewport and Scanline render look correct but Arnold renders the full gradient map on each particle shape.
The change happened after MAXtoA-22.214.171.124, when reverted back to this version the result is good.
This can be validated using the Tyflow example scene tyFlow_UVWGradient_001.max.
I have also tested this with the latest version (MAXtoA-126.96.36.199)