Cannot create custom field on Opportunity Contact Role object?

According to SFDC documentation, you can create custom fields on the Opportunity Contact Role object. 

https://help.salesforce.com/s/articleView?id=sales.sales_core_opp_contact_setup_customize_lex.htm&type=5

https://help.salesforce.com/s/articleView?id=sales.sales_core_opp_contact_roles_considerations_customization.htm&type=5

However, I am trying to do so and on the last screen (after selecting the page layout to add the field to), I get the following error.  Has anyone been able to add a custom field to the Opportunity Contact Role object? 

Unable to Access Page
The value of a parameter contains a character that is not allowed or the value exceeds the maximum allowed length. Remove the character from the parameter value or reduce the value length and resubmit. If the error still persists, report it to our Customer Support team. Provide the URL of the page you were requesting as well as any other related information.

The test field was a simple checkbox with a label of true.   

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