Javascript server error when enabling and refreshing live Preview from iPhone

I've been getting these JS pop up errors every time I refresh my iPhone Safari browser that's running from the IP address in Preview mode. They look server related rather than any errors to do with my site's JS.

The same error appears up to 4 times in a row before being accepted and rendering the webpage on my iPhone

JS server error popup

I get the exact same error on win8.1 desktop using FF (ver. 45.0). I usually load up Chrome with the IP then copy/paste it into FF. I only get it the initial time I load the page, refreshing doesn't cause the error. The error seems to be attached to the app according to where the error windows task window appears.


jep.. so I have

sometimes on linux with firefox. chromium works fine.

Firefox is getting more an more worse... it slow, slower, most slow, and crashs often.

I could not reproduce this error... sometimes it appears, as IO wait for it... FF is playing Murphy with me