Hubspot: Random authentication warning/error even when logged in

[gerrit-de-heij]

I have installed the Umbraco.Cms.Integrations.Crm.Hubspot package version 4.0.3 on Umbraco 13.5.3 and have this strange issue where the following authentication warning/error randomly shows when opening the HubspotFormPicker widget in the BlockGrid:

This even happens when I'm logged in into Hubspot. When I go to the data type of the form picker, it shows that I'm logged in:

When refreshing the page a few times, the error goes away for a while but randomly shows again. I can't select a form when the error is shown, which is not very user friendly.