The beta firmware will simply be overwritten when flashing the modified one. The beta app should work, but it will possibly complain about the (in its eyes) outdated firmware.
I don't own a C5, so I cannot test this myself.
Thanks I'll check out the updated firmware. I have installed the beta app and firmware already, do I need to uninstall that first?
That are compression artifacts, which are caused by the amount of objects in the video (many bushes, trees, leafs, etc.). Look at the street right after you passed the steamroller. It looks way better than at the beginning of the video. That's because, after the steamroller, there are less objects in the video to encode.
The K2 does have the same "problem". That's why I modified the firmware for the K2 to increase the bitrate and reduce the compression artifacts.
And as someone asked for it, I've made a modified firmware for the C5, too.
Just take a look at the thread in the K2 forum.
There you will find the download link to the modified firmwares. Within the link there is also a video comparion, showing the difference between 12 MBit and 20 MBit bitrate. Don´t watch it online, as the quality may throttle, depending on your internet speed. Just download it and watch it on your pc.
There are two original V.047 firmware for the C5 on the offical download page. One of them is to support 256GB cards. I don't know on which version my modified firmware is based, but I guess it is the normal one without 256GB support. So for a test you should not use a 256GB card.
If the modified firmware resolves your issues, I can modified the 256GB firmware, too.
Blocking tends to be more noticable on road and sky.
Unable to upload a 60sec vid as it gets stuck at 99% so I hope a still will do.
Don't have an answer can you post a bit of the video to show what the problem is?