We found an issue with Builder's UI when you change the padding of an element. When you do not close the the pop-up bubble and move on the next viewport, the values on the padding do not refresh. This happens also even after saving the settings for a particular viewport. -> then moving to another one. Assuming that paddings in Tablet were already set differently from the Desktop, on desktop layout -> click responsive button -> then click tablet, the form remains open but the numbers do not change.
This happens on Mac and windows browsers where the server is a local machine or hosted on the cloud.
From a UX standpoint, it confuses the one working on the layout. Then secondly the values being saved will be incorrect. Obviously the solution was to close the adjust padding popup first however, imagine the amount of time figuring out dealing with these sort of issues that we find on builder.
On a slightly related one, it would be good if builder will warn the user to save the element settings for a particular viewport before a user clicks another. Or probably disable the other responsive icons until the user clicks Save (making the save button more obvious). The present UI invites a users who is gung-ho to click and click without realising his data hasn't changed at all.
We would be able to suss things out ourselves but realising the tremendous amount of time we spend on just solving issues, we felt that we need to call your attention. We spent heaps of times guarding what and when builder is saving files in the theme folder and data on wp-post table. This is just to learn the behaviour of the system.
We could post a support ticket but sorry to be blunt - we often come across on searching the WPMU Dev's public support tickets that the issues cannot be replicated and we find no answers after a request from your side to login to people's wordpress site.
We do not need further support on this but kindly consider our suggestions.