Spark email HTML viewing issues?

Been giving Spark email another try. I am liking some of its advantages over Apple Mail and Outlook. However, I am experiencing some HTML rendering/viewing problems that are fairly annoying. Bold and italics render just fine, but if an email has any underlining in it, reading the email Spark on iOS seems to change everything to plain text (albeit with the underlining - and only the underlining – intact). This issue doesn’t happen on Spark desktop.

However, I did notice on Spark desktop that any highlighting of text does not show when reading (although when I format and send it that way in Spark it shows up correctly in other clients).

Is this a known bug? Have any of you encountered, and is there a fix or setting or something?