Framerate cap not 300 as patch note says, actually locked to 144 again.

Two main factors i can think of to check.

1. Do not use any other fps counter other that origin as they tend to cap at 144.

2. Disable v-sync settings in the Nvidia control panel in the 3D settings section for individual programs.

If it still caps on 144 try this in the command arguments: +fps_max unlimited