Yea, it seems that whatever was causing the hang is fixed in this new build normandc suggested I should try. Maybe it should be revisited later if someone discovers other weird things happening which could be related to this issue.Yes i agree it is s bit strange you are able to create both horizontal/vertical mirror for Groove feature this way. Maybe that does indicate i is not just the OCC/OCE fault but i guess what ever is the cause got fixed in newer version of FreeCAD or OCC/OCE. At least for the crashing part.
My new build info:
OS: Windows 7
Platform: 32-bit
Version: 0.14.3343 (Git)
Branch: libpack
Hash: 8dcb8f68cf17ef152d34d226d7699c98c5bb59fb
Python version: 2.7.6
Qt version: 4.8.5
Coin version: 3.1.3
SoQt version: 1.5.0
OCC version: 6.7.0
Yep it seems to be a problem related to snap. I could reproduce it even in this new version but only if snap was active. It is still a bug, right? I suspect that it could happen to other cases not just groove on my model since it is caused by snap.I guess it failed because you used snap mode again and when entering that corner case scenario as seen on image that causes the issue with refreshing the groove feature. Try on newer version as it was suggested and if it will be still there maybe this is something for bug tracker. But i guess that crashing part should be gone.