I would
dbstop at matlab.graphics.internal.copyFigureHelper 145
and see what argsToPrint{4} is, and then start tracing back to see how it got that way.
Which MATLAB version are you using? In R2017b, that code is at a different line.
Also, check
which -all print
You should see toolbox/matlab/graphics/print.m and a number of Java methods, and one built-in method. I suspect you have your own print.mexw64 or the like.