FFMPEG handling h264 stream that does not send a frame consistently

Question

I am working with a raw h264 stream, this is a live stream coming from a device, however when the device is streaming a menu page that is static, it doesn’t send out a frame. I am feeding the stream back into a v4l2 loop back instance and then consuming this on a webpage via getUserMedia. The issue I have is that ffmpeg does not send frames to v4l2 when the hardware device is not sending frames. I have tried to set the output of ffmpeg to cfr and 60fps. However this doesn’t make it send out duplicates of the last frame. Is there anyway to achieve this?

Thanks in advance