Digital television does not work on Kaffeine after the latest updates, and I have found out that the problem lies with v4l-utils. Downgrading v4l-utils solves the problem. However, I am aware that using Downgrade is frowned upon when using Manjaro. Is there any way to solve the bug?
Known bug and already reported on Arch Linux side. According to this ticket, Arch Linux and Manjaro are not the only distros affected.
Downgrade is a tool made primarily for Arch Linux, not for Manjaro, and can be misused if you are not careful. Ideally, you should restrict yourself with packages available in your cache (by default: /var/cache/pacman/pkg) so you are absolutely sure to have packages that did appeared on Manjaro at one point or another. However, since v4l-utils is a package imported from Arch Linux, if you absolutely need to get a package online (for example, because you do not have older versions in your cache), it should work okay on your system.
Do not forget that downgrading in general is merely a temporary workaround and that it should not be kept forever. Keeping it for too long may become an issue in itself in the future.
I don't know. I would say that unless you have some programming skills and that you can either suggest a change for v4l-utils or Kaffeine, there isn't much you (or we, also) can do about it outside of waiting for an update from upstream.
If someone has a better idea, feel free to suggest.