Is this border-variation a bug?

So far I’ve never encountered a bug in Sparkle, but I think I found one now.

In the screenshot underneath you can see the same form twice, on the left with “single line” unchecked, on the right it’s checked for the Message-field. As you can see this changes the border, on the left it’s rounded, on the right it’s angular. But in both case the border-option wasn’t checked at all.

Am I right, and is this a bug?

Possibly yes. Please send the project file and we’ll take a look.

Just sent you the project file.

In the meantime I looked a bit more into this and realised that on the desktop the rounding corners don’t show up (so it is as it should be), but on my iPhone it shows in all browsers.