Tpmfs /run 100% used

Hello I have a problem with my VPS that runs a wordpress blog. When tmpfs / run reaches 100% usage my database stops working and I need to restart the server. Then tmpfs / run goes to 0% and everything goes back to work until it reaches 100% again.
In / run I have nginx-cache folder which is occupying the space. How do I fix this problem? Is it a configuration error?

df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            465M     0  465M   0% /dev
tmpfs            99M   36M   64M  36% /run
/dev/sda1        19G   12G  6.6G  64% /
tmpfs           493M     0  493M   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           493M     0  493M   0% /sys/fs/cgroup
tmpfs            99M     0   99M   0% /run/user/0