Why are my heating emitters square?

Hi guys, rather new to Hevacomp so apologies if this has been asked before or is a simple one.

Loading up a test project this morning I've found that my heating emitters are showing as square rather than rectangular.

 Then when I move the emitter it highlights as expected, rectangular - 

This wasn't happening yesterday so I expect I've accidentally changed a setting somewhere.

Here are my current settings - 

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