It appears as if escaping the braces by doubling them up is not working properly if the braces are in a format specification within a f-string.

>>> print(f'Email:\n    {C:{{v.name}} {{v.email}}|\n    }')                         
Traceback (most recent call last):
  File "bugreport.py", line 95, in <module>
    print(f'Email:\n    {C:{{v.name}} {{v.email}}|\n    }')
NameError: name 'v' is not defined

The escaping works as expected when the string's format method is used.