How do I fix/avoid AADSTS650051: 'dynamicPermissions' is not a valid parameter for 'consentToApp' that some users get when trying to login with AAD?

I have a bare-bones website (single page app) that tries to log in the user with AAD using the msal JavaScript library. It is practically just doing what the example AAD login code does:

1. It creates a UserAgentApplication with my app's client ID and the authority URL for my tenant
2. It calls handleRedirectCallback and loginRedirect
3. It tries to get either the accessToken or the errorCode/errorMessage from the redirect response

Under practically all circumstances this works fine. Users visit my page, they get redirected and login just fine. One particular user, however, after the redirect and attempt to login gets this error:

Login failed: invalid_client - AADSTS650051: The parameter 'dynamicPermissions' in the request payload is not a valid parameter for the function import 'consentToApp'.
Trace Id: ed33266a-26ac-4706-9018-e6e89f650100
Correlation Id: e3103cab-1a7f-4a99-8455-fd8c8a769e35
Timestamp: 2019-06-25 20:50:44Z

He has tried this in many different browser (Edge/Chrome) and always gets this error, even in InPrivate/Incognito mode. No other user ever runs into error that I've found.

I'm not sure how to debug the issue because in my code I don't ever specify a 'dynamicPermissons' property or reference a function named 'consentToApp.'

How can I troubleshoot what is causing this error for this one user?

Thanks!