I don’t know if this problem persists in “higher” versions of Rhino… (I’m still using 5.0 ;o(
but it seems strange to me that an RMTL file created/modified externally (I used Octave, because saving TXT from Grasshopper is too difficult…), is not accepted by Rhino if it is not UTF-8-BOM.
Is there a reason for this choice?