/run/user/1000目录归属异常引发Snap及系统相关问题求助

大家好，我最近碰到了一堆和Snap相关的故障，查了半天发现根源似乎是系统里的/run/user/1000目录权限归属出了问题，想请各位大佬帮忙支招。

首先，我执行了这个命令查看显示管理器状态：

systemctl status display-manager

得到的输出里有这些关键错误信息：

gkr-pam: unable to locate daemon control file
gkr-pam: stashed password to try later in open session
pam_unix(gdm-password:session): session opened for user jhon(uid=1000) by (uid=0)
pam_systemd(gdm-password:session): Runtime directory '/run/user/1000' is not owned by UID 1000, as it should
pam_systemd(gdm-password:session): Not setting $XDG_RUNTIME_DIR, as the directory is not in order.
gkr-pam: gnome-keyring-daemon started properly and unlocked keyring
Gdm: process -888 was already dead.r

其中pam_systemd提示的/run/user/1000不属于UID 1000，导致$XDG_RUNTIME_DIR没设置，我怀疑这就是Snap问题的源头。

现在的Snap问题具体表现为打不开Firefox，启动时会弹出这些错误：

cmd_run.go:1055: WARNING: cannot start document portal: Expected portal at "run/user/1000/doc", got "/home/pablo/.cache/doc"
/user.slice/user-1000.slice/session-2.scope is not a snap cgroup

我试过用chmod修改目录权限，但完全没用，实在不知道该怎么办了，求大家帮忙！

备注：内容来源于stack exchange，提问作者P2000Gua