CentOS

Not surprising if you don't have a network connection:
Download it on another machine, transfer it and then use rpm to install it.
And if you have network, first install ELRepo.

Is it a long time since you have rebooted? - a new kernel requires a reboot.
Also, CentOS 7 dies in three months time.

Deleted - didn't see Trevor's answer.

What's your RAID cards?

And if security is a concern, then Stream may not be the best choice:
Stream is a rolling pre-release (aka. beta) of the next RHEL point
release. It may be better to use one of the RHEL clones/rebuilds like
Rocky, Alma, OEL etc.

Looks like it's missing, on a fully updated system I have gstreamer1-plugins-bad-free from April 2018.

I guess Trevor already gave you an answer, you have to check your repo-files.
Alternatively output from yum update may help.

What's your CPU?
Does it also happen with older kernels?

Never used pika, but I doubt that you need/should back up /dev.
How did you configure it?

Edit: And how much data, and at 50% what folder are you backing up?
Any logs that can tell you something?

It may help if you say what hardware you have.
You should be able to ssh into your system from another device.
Also note that Stream is a rolling pre-release (aka. beta) of the
next RHEL point release. You may be better off using one of the
clones/rebuilds of RHEL like Rocky, Alma, OEL, etc.