Kentico 13 pagebuilder consistent error on multi-site instance

On our Kentico MVC instance, we host 5 sites. We are getting an intermittent, but consistent error in the page builder. It seems to happen when switching between sites in the drop down menu. It's inconsistent,in that it doesn't happen every time, but I am able to reproduce it within 5 minutes of trying. On loading the pagebuilder, we receive:

and in the event log:

Event ID:5745511
Event type:Error
Event time:15/03/2023 12:21:25 PM
Source:Application_Error log, exception in application
Description:Message: Try reloading the administration interface. The user was not found in the JWT token, nor in the current virtual context URL.

Exception type: CMS.Helpers.InvalidVirtualContextException
Stack trace:
at Kentico.Content.Web.Mvc.VirtualContextPrincipalRetriever.GetPrincipal(String jwtToken)
at Kentico.Content.Web.Mvc.VirtualContextPrincipalAssigner.SetVirtualContextPrincipal(IVirtualContextPrincipalRetriever virtualContextPrincipalRetriever)
at CMS.Base.AbstractHandler.CallEventHandler[TArgs](EventHandler`1 h, TArgs e)
at CMS.Base.AbstractHandler.Raise[TArgs](String partName, List`1 list, TArgs e, Boolean important)
at CMS.Base.SimpleHandler`2.RaiseExecute(TArgs e)
at CMS.Base.SimpleHandler`2.StartEvent(TArgs e)
at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Like I said, it seems to happen when we switch between different sites in the drop down and load the page builders too quickly. Obviously, I have tried reloading the application interface, but once we receive this error, the account seems to be in a messed up state. We have had luck logging out of all the CMS's except for the one currently being worked on - sometimes. If all else fails, restarting the MVC azure app service resolves it.

Things that don't work:

• trying a different browser or incognito window
• logging out and back in to the CMS
• switching to a different site in the CMS and back

This is happening to our devs, QA team, and client. It's becoming increasingly frustrating for them. Any help would be appreciated.

Per Brenden's questions below:

The sites share a CMS, and each has it's own cloud-hosted azure app instance. So 6 app instances per environment (2 environments currently, DEV and UAT). No firewall or WAF is in front of the application, and all sites are using SSL.

Things to verify in your application setup:

• Verify your hash string salt is the same for all MVC site code AND the CMS instances
• Verify you have the proper domain license keys
• Verify you have the proper site presentation and administration URLs. If they are on different domains, make sure you are specifying that and have those proper license keys.
  -- For instance devadmin.mydomain1.com (CMS) and https://dev.mydomain1.com (presentation) need to have both license keys AND added in the site as the proper domains.
  -- Also for the other sites you can have something like devadmin.mydomain2.com and https://dev.mydomain2.com
• If you are running domain aliases, be sure those are aliases and NOT in your site General definition. For instance, using localhost, put that in the Site > Domain Aliases and not in the actual definition of the site on the General tab.
• I'm assuming you're using in-proc session storage, you may want to generate a machine key and add that to your configuration files OR use something like SQL Session or Redis Cache to handle the session within the CMS.