Trace reference scale showing incorrectly

[KM2]

I have a problem with the scale of a trace reference- its magnified about 100, maybe 1000 times the size its meant to be!

I have a floor plan layout and I'm trying to show another layout as the trace reference to align them on the page. 

The scale of the trace referenced page is so large the text from the title block  is showing in huge orange letters.

I've tried closing and reopening the file and 'rebuild reference' and 'reset to default position' from the trace reference dropdown. can't think of what else to try.

Thanks in advance for any suggestions. 

Operating system used: Mac Intel-based