Unfortunately, this is a byproduct of the denoiser used by Twinmotion to remove the noise from Path Tracer renders. While the denoiser tries to remove as much noise as it can, and it does a fairly good job at it for still images, it unfortunately isn't as good at denoising videos and can leave behind these flickering artifacts.
The best way to remove noise is to increase the Path Tracer's samples per pixel and max bounces setting, which improves overall image accuracy and results in less noise. This will increase strain on the graphics card proportional to the amount the settings are increased, and increasing the settings too much can cause your graphics card to crash. Your rendering times will also increase proportionally, so keep this in mind.
An alternative solution would be to export your video with the denoiser disabled. You can then run this video through a third party denoiser tool, such as Neat Denoiser to Adobe Premiere or Davinci Resolve's denoisers tools, which may yield better results.