The editor does a very weird over shifting, starting in my case in character 29 and seems to fix itself after the 45, the cursor gradually starts to appear over the character instead of between the characters, making several leaps (several character ahead of the actual editing point) and it makes a mess of what you are typing, as it is totally out of focus:
Here are the screenshots
did you solve this issue? I'm having the same problem in OSX 10.11
Which version, OS, font are you using?