thank you for the further details. It is more clear now.
From technical point of view, a single font can't contain multiple equal glyphs with different sizes. For example, it can't contain the glyph 'e' in a small and large version:
It seems to me as if one of the following options is true:
1. The field 'First name' is configured with another font. Check once more the initialization of the fields.
2. The font for the 'Field name' is changed dynamically at the runtime within the implementation of the form. Maybe in your implementation you assign another font to the fields?
3. The used font is overridden by a variant and this variant is switched on (or off) dynamically at the runtime after the fields 'Patient Id' and 'Last name' has been initialized and before 'First name' and 'age' have been initialized. This would mean that your application uses the Styles to switch on/off the variant. Is this the case?
Does one of the above options apply to your actual implementation? If you can't find the cause of the problem, you can upload an example demonstrating it.
Concerning your first question, if you observe the delay during the prototyping only, this delay is possible. This is because during prototyping the font resources are converted just in the moment when the font is used for the first time. If this is what you observe then don't worry, the delay will not appear in the target system. It is just an effect of how the prototyper handles the resources internally.