Hello!
Well, we have it that Sencha has fixed the issue but seems it is not really feasible the fix for the previous ExtJS 5.x version, or at least so they deemed by fixing just to 6.x series. That said, I will be following up to their status and will close this issue here.
If this really still bugs you on 3.x version we can also try to open the issue on ExtJS 5.x series (if we can consistently reproduce the issue on a
sencha fiddle, preferably) and well, wait and see what is their position about fixing in ExtJS 5 series (thus Ext.NET 3).