EMQX Dashboard Overview Charts Issue

I am using EMQX Enterprise Edition, version 5.3.0 for testing purpose, in a 3-node cluster.
I find the charts to be completely unreliable.
The numerical indications are correct but the corresponding graphs are wrong.
For example:
Numerical : All connections 7, Live connections 7 Chart Connections 5
Numerical : Topics 526, Subscriptions 526 Chart Subscriptions 521

Is there any explanation for this ?