vzquota : (warning) block_hard_limit [102] < block_current_usage [520824]
This is because your disk usage of the container exceeds the quota.
Eg. once on a test container I had accidentally set it to 32MB yet the OS took about 600MB.
Just set the quota to something bigger than the currently used space to solve it.
vzctl set 3891 --diskspace 5G:5G --save........