Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 456.71
Broken: version: 2.92.0, branch: master, commit date: 2021-02-24 16:25, hash: rB02948a2cab44
Short description of error
Joining two or more curve objects together will result in the curves being assigned the active object's material rather than keeping the material assigned to their points.
Exact steps for others to reproduce the error
Open the below file:
Use Ctrl+J to join the two curves together.