Sometimes the plugin cannot be initialized ERR6 after Cannot read properties of null (reading 'contentwindow')

This ticket refers to the customer ticket 56816.

In a Haiilo instance of our customer, sometimes the Haiilo plugin cannot be initialized. In the console you can see an ERR6 with the error message "ERROR PluginError: Initialization timed out after 60000ms (ERR6) at 672.5ce4467c03910880.js:1:15927". If the page is reloaded in such cases, the plugin is initialized correctly afterwards.

Noticeable is that before that another error message "Uncaught TypeError: Cannot read properties of null (reading 'contentwindow')
at init.js?id=0fa78adf...7&lang=en-US:185:78" appears and then after 60000ms the ERR6 code appears. I have two screenshots showing the behavior.

I myself, cannot reproduce in our Haiilo test instance the problem. Here the plugin is always loaded.

Where does the error "Uncaught TypeError: Cannot read properties of null (reading 'contentwindow')
at init.js?id=0fa78adf...7&lang=en-US:185:78" and do you think this error is related to ERR6?

Thanks,
Simon