Thank you @mekkablue.
I‘ve also noticed that Glyphs 3 is not fond of straight curves with handles. The highlighted part (waist in Bold master) breaks the Remove Overlap filter (unless I move either of the handles at least 1 point sideways). Attaching the file also.
Here is another test file that fails in Glyphs3 v3041. This one worked in some earlier versions, around 3034 or so. RemoveOverlapTest1.glyphs (6.7 KB)
The culprits seem to be the two nodes on the crossbar of the T that have a handle located almost exactly on the outline and very close to the node.
My previous test files works now in 3.0.2 (3041), but this test-case fail: Test.glyphs (3.5 KB)
Getting a lot of those too - even in letters that have no overlaps to remove.
I believe each of those test cases will work in the next release, @chrisjansky, @lvcivs, and @FlorianPircher. In a version after beta 3.0.2 (3041). Thanks for the test cases.
I had this today with a number of ligature glyphs in a font, and it prevented me exporting it. In the end I had to export it as a UFO, open it in Glyphs 2, remove overlaps, and export it from there. The revised file still wouldn’t export when it was opened in Glyphs 3 again, with no overlaps.
I noticed that each of the problematic glyphs had elements where Glyphs 3 had put a kind of carapace of Tunni lines around them. I don’t know what this is (or how to turn it off), and I realise that in areas that are affected by it I can neither edit the Bezier points and nodes, nor will ‘add extremes’ work. What is this? (Otherwise totally loving Glyphs 3.)
[Using the latest cutting edge version, 3.0.2 (3044)]
Perhaps try Convert to Cubic on them?
You don’t need to use ufo to exchange data with Glyphs 2. Just set the file format to version 2 in Font Info > Other.
Error message in G3 3.0.2 (3050) on export (macOS 10.15.6):
Something went wrong when removing Overlap in Glyph: G
I deleted all overlaps here, but the error still occurs.
It exports well in G2.
Konsole_G.glyphs (22.0 KB)
Thanks for the file. I fixed the problem.
G3 3.0.2 (3050)
the problem is still present:
Something went wrong when removing Overlap in Glyph:
with G2 it works.
But copy&paste doesn’t work anymore and backwards compatible doesn’t work either!
Can you send me that glyph?
Hello! I have also this problem when I try to export the font. With Glyphs 2 this problem didn’t exists.
I also made all the updates but unfortunately the error message still appears
Any ideas out there to help me? Thanks 
Have you checked the path direction? It needs to be counter clock wise. Running Path > Correct Path direction should fix it. If that is not fixing it, can you send me the .glyphs file?
Thanks for your answer. Yes, to my knowledge the path directions should be okey. I’ve sent you the file…
I’m also getting the same error with [3065] when exporting Cormorant Bold (link).
BTW, I batch-generated the Cormorant fonts with a script and Glyphs 3 didn’t report the error. I only noticed because the modify dates hadn’t been updated on the Bold fonts. I do get error reporting when I export by hand via menu command.
This is happening in 3065 indeed. @GeorgSeifert I’ve sent you a file to see if you can reproduce it - specially with Hbar/Tbar
I just uploaded a new version that improve the remove overlap and your file should work now.
In version 3066? Can you send me that glyph?
