Text editor (Files sub-application) size, colour, font, & typographic emphasis bug

When I write custom text annotations on different pdf files in iPhone's "Files" app, the text will change from the specified values (size, font, colour, and typographic emphasis) to a text size much smaller, font change to Times New Roman, colour change to black, and unemphasisyd text.

Why does this occur and is there a way to solve this error or a work around until it is fixed?