I posted in your previous thread about a possible solution that helped with my new neck re: the high e string slippage.  I don't know if it will help much with the original neck but may be worth a try.  I adjusted the set screws on the bridge saddle of the high e so that it was angled in towards the middle of the neck.  This actually had the effect of moving the string slightly, on my warmoth neck it had a huge impact, partly because that bridge saddle seemed to be setup in the reverse when it arrived (angled outwards) and partly because my neck is slightly wider at the nut but it may still have an impact and it's worth a try.  You can still achieve the same string height  even though the saddle is sitting on an angle and for me anyway the string doesn't slip out of the groove.  But that little adjustment has pretty much eliminated my high e string slippage.

I don't think it's ideal, of course it would be better to offer a solution of a replacement bridge plate that places the saddles a little closer together so that we can get the strings away from the edge of the neck and we don't have to angle the saddles.  a) it's probably better to have the saddles level, and b) it would probably  bring the string in further from the edge than simply angling the saddle.

They have a great product here, it needs a wee bit of tweaking, but I love the flexibility I have playing live now, and even recording.  If Line 6 could just work on offereing some fixes it would make the playing experience that much better.   And I think moving forward they should offer a few neck variations on each of the models '59 '69 and maybe even '89.  I haven't played an '89 but both the '59 and '69 have fairly chunky necks which guys with bigger hands may like but there are a lot of guys that would prefer a thinner neck.  I know the models are of vintage guitars and they have put vintage feeling necks on to match (I guess that's why, who knows really).  But it would be nice if they even offered some newer guitar models that would be an update in workbench that you could load into the JTV if you wanted.  OK, now I'm just rambling.