Google jsonp intermittent 404

Anyone noticed they are getting intermittent 404 ( not found ) when using the google json hack ( Google Sheets > json fetching )

$.getJSON(feedurl_start+"worksheets/"+feedkey+"/public/basic?alt=json", function(sheetfeed) {

I have never had any issues with using this over the last few years but a couple of weeks ago I started getting 404s on the getJson() calls.

This gradually got worse on some of them.
I think it may be to do with some back end changes google are making to public file access. I do not think the way the jsonp hack accesses the public files ( google sheets) was meant to be affected by their changes and it is just unforeseen collateral.

I have now changed my code to fetch the csv data rather than json.

This was not a major change to my main body of code.

Just wondering if anyone else has been seeing this?