When I open Aximmetry and select the project, I can maintain the frame rate I selected at first.
But after a while, Aximmetry will drop the frame and it will remain at 25p.
Or sometimes when I switch other applications, frames are dropped. The way to restore is to reset the camera device and then select the device. Aximmetry will return to the frame rate I selected but it will not last too long.
And I found that GPU utilization is the key to affecting the frame rate. If the utilization is high, it can always be maintained, but if the utilization is low, the frame rate will remain 25p. I don't know whether some settings of the graphics card cause the low utilization of Aximmetry, or the low utilization of GPU caused by Aximmetry itself.