Why have I been intermittently getting 504 gateway timeout errors?

This hasn’t happened for about a month… so I assumed whatever issues were happening were solved but this happened again today. I have two clusters and when this happens I’ve figured out that I need to move the data from one cluster to another and when it happens again I have to move it back to the other cluster. I don’t know if the information below is helpful because it doesn’t seem to matter as it has happened on both. It appears when one cluster is timing out, the other one appears to work. Hope this is helpful.

Cluster 1:
VERSION
7.0.7

REGION
AWS / Oregon (us-west-2)

CLUSTER TIER
M0 Sandbox (General)

Cluster 2:
VERSION
7.0.7

REGION
AWS / N. Virginia (us-east-1)

CLUSTER TIER
M0 Sandbox (General)