$w.onReady(function () {
let data = $w('Button')
let dataLength = data.length
console.log(data)
console.log(dataLength)
});
This code-Snipet works perfectly in the Preview-Mode, but do not really work on live-site.
Preview-Mode:
-fast running code
-shows results in console
-everything seems to be normal
Live-Site:
-very slow code-operation
-no results in console
Just after few seconds the code ends running (without any info of results)
It was wiser to post in the Rolling Out New Improvements post because, it works fine for me →

Ok…
information-update.
It takes about 50-55 seconds to get the results back from console in this code.
$w.onReady(async function () {
let data = await $w("Button");
let dataLength = await data.length;
console.log("Data-Length = " + dataLength);
for (var i = 0; i < data.length; i++) {
console.log(data[i].id )
}
});
works (results are showed after 50-55 seconds on live site in console)
console.log("Data-Length = " + dataLength);
-dataLenght is correct. (correct counting is working)
Also it works in PREVIEW-MODE (much faster 1-sec), but counting is WRONG!
Do not recognize all elements on stage.
works on LIVE-SITE (needs as already mentioned about 50-55 sec. to show the results of console-log.) Shows also all IDs of all found elements.
Counting is correct.
for (var i = 0; i < data.length; i++) {
console.log(data[i].id )
}
But do not work correctly on PREVIEW-MODE (do not recognize all elements on stage) ----> WRONG-COUNTING of ELEMENTS.
This one do not work on LIVE-SITE
console.log(data)
…OK FORGET IT!!!
IT WORKS AGAIN!
Great work wix! Very fast reaction!
Yes, right now it works again, also for me.
And yes, it was posted also into Rolling-out-Thread. 
Seems, that someone has already took a look on it.
Since yesterday, i had this problem.
But PREVIEW still do NOT give the same results as in LIVE
Ok, i think i found the bug.
It seems to have problems when adding some elements from “myDesigns” to stage.
After input of some elements from “myDesigns” the elements will not be recognized.
But when creating manually new buttons, it works.