Character replacement icons in Grbl console

I purchased a Chinese “TOPQSC 7000mW” laser from eBay, it worked fine with lightburn but the controller it came with didn’t have contacts to install limit switches.

So I bought this Arduino nano controller from eBay ( However after installing it I noticed messages from the controller in the console have the replacement character (questionmark in a diamond) randomly occuring a lot of the time. I tried another usb cable and different port but this didn’t fix the issue. Does this mean I have a faulty controller or could it be something else?
Here’s a picture where sending the “?” Command results in a different outcome each time lightburn

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