System Information
Operating system: Windows 10 x64 / Linux (Deepin) x64
Graphics card: AMD Radeon Vega 8 intergrated graphics

Blender Version
Broken: 2.90.0 release 0330d1af29c0

Short description of error
If a 3D viewport was opened by splitting an area vertically, then the cloth filter brush will only make mesh float upwards when dragging the mouse in either direction.

Exact steps for others to reproduce the error
0. In "Sculpting" tab of the attached .blend file (the right side viewport was opened by vertically splitting the left side viewport), use cloth filter brush as described.

More details provided in the video.

File: