Up Mini 2 - printing features

Hello, Up Mini 2 users!

I’m used to print 3D stamps from company logos. My issue is that I cannot control whether the result is hollow or not. For instance, if the logo contains any letter, then these would be printed hollow (vs if it contains a picto, the picto is printed plain).
Is that a settings issue or rather an issue coming from the original 2D picture file I convert to 3D?

Thank you very much!