Adding LXC id mapping reverses ownership of all user-owned files within the container

I'm using LXC within proxmox.

I’d have some bind mounts I’d like to share between a number of LXC containers. Also like many, I stumbled upon the problem of conflicting UIDs. I'm trying to do a very typical uid mapping. I have both a Guest and Host user id 5000.
Just for reference I'm adding my config, it is valid, because it works. I see Bind mount files on Guest/Host owned by #5000 user as their respective users in Guest/Host.

lxc.idmap: u 0 100000 5000
lxc.idmap: g 0 100000 5000
lxc.idmap: u 5000 5000 1
lxc.idmap: g 5000 5000 1
lxc.idmap: u 5001 105001 60535
lxc.idmap: g 5001 105001 60535

sub{g,u}id
root:100000:65536
root:5000:1

BUT. When the mapping is added, the /home folder on the Guest is suddenly being owned by 65534/nobody. How? Why? What could be the possible issue?
I tried the same with multiple container templates (Turnkey, Alpine) with same results...

Are you using random UID's and GID's instead of actual ones?

No, they are both valid users. I updated now the original post to focus on the main issue - even with the mapping basically working, /home becomes owned by nobody.