I will quote my colleague's reply to your support ticket on the same subject:
"Can you provide us with more details as to how the deployment was configured. Did you use the automated Thunder procedure
and follow the steps through there.
Was the project deployed on Azure before and when issues suddenly started to show up?
There is one potential resolution to this: There seems to be a known issue with Azure's timezone settings. Whenever Azure resets their VMs they reset the Timezone to UTC(Universal Coordinated Time) I believe, which then may result in the embedded resources not being served, because the timezone at build time doesn't correspond to the timezone on the server.
Can you try redeploying the package after you set any time zone in the back end and let me know if this works."
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