Is this a known bug? I just upgraded to cutting edge hoping that would resolve the issue but it hasn’t. It crashes when values are copied from an existing rmx scaled glyph or from a text file. It was working previously, only other thing I can think of is that the number of masters in this file grew to four from two and contracted back down to two. Just an idea as I know master numbers has been an issue in the past.
I installed the latest RMX plugin.
osx 10.10.5 glyphs 2.6.4 (1273)