Temp displaying "?" Instead of minus "-"

I am using a watch face that is displaying the temperature as “? 5•C” instead of “-5•C” . For some reason it seems like the minus isn’t understood, so is displayed with a question mark. Does anyone know how to fix this?

I messaged the watch designer about this who told me to message Facer support, but haven’t heard anything yet. It’s a bit frustrating because this is the first one that I have purchased, and then find when the temp drops below 0 degrees, there is a bug. Has anyone else experienced this?