Hey there! Just updated my glyphs but transformations (mirroring) are not working now. This dialog pops up when I use mirroring.
What version do you have now? And what did you try to transform?
Hey there! It is Version 2.5b (1078)
I am transforming normal outlines. I have tried transforming components, combination glyphs and outlines. That dialog keeps coming up. My OS is:
macOS Sierra Vers. 10.12.6
Cannot reproduce. Can you describe steps to reproduce the problem?
Hey there!
I filmed it with my phone here: https://www.dropbox.com/s/wczzqjc08nx37gf/VID_20171101_220759.mp4?dl=0
I have had it too once.
What did you do to fix it?
It only occurred with some components. I could only mirror them through Python scripting, or through workarounds (like rotating, or entering -100% scale in info box).
-100% will have to do for me now 'till this gets resolved maybe on the next update. Mirroring works on my iMac with an older operating system though! Maybe this is an OS specific issue?
Can’t use the -100% 
glyphs won’t let me
Sorry it does work, but for components only
Working now! I just some updates to my Operating System and now mirroring is working. Thanks @GeorgSeifert and @mekkablue for your help!
Interesting. Which OS are you running now?