Power Chart Not Updating

We are using 8.1.23.
We have a power chart that linked to a couple opc tags. Everything works normally for a few days. The data is updating properly in realtime. Sometime the data would stop updating. The chart would show the data holding the last value for 10 mins or sometime 30 mins.
We had other projects running on the same gateway and historians at the same time but not seeing this issue.
Any idea of what could be the cause of this issue? Or where to look for debugging?
image

Are those other projects accessing these same OPC tags and history without issue? Or are they accessing different tags? Do these tags show any kind of error in the designer tag browser during this time?

Have you tried trending a different set of tags on this project? Is the problem local to only these tags on this project? Or is the problem across these tags but on multiple projects?