IE11 + Edge 12-13-14 : random JavaScript parsing errors, caused by very long object?

I'm getting reports of JavaScript errors in production (from TrackJS.com) from IE & Edge browsers like:

• Expected identifier, string or number
• Unterminated string constant
• Expected ':', '}' or ';'
• illegal character

And when I check the error file / line, it's sometimes in "mathiasbynens/he" library (look on GitHub), like here : example 1

And sometimes it's in other parts of the code (like in YUI library). I've got lots of these and they seem completely random (targeting what seems to be valid code) : example 2

The only idea I have would be that IE shits on himself when loading the very long JSON defined in he.js. Have you ever had any issue of this kind ?

Thanks a lot for your help. gnutix