When creating a new site you need to click on the 'save' button to save the site for the 1st time -
After the 1st save - The editor is set to auto save after each change.
Once several changes are saved within a very short period of time, it may disrupt the saving function and cause that not all of the changes are saved properly.
Please allow several seconds between changes.
You need to see that the save icon is giving an indication by showing the word 'saving...' and then 'saved'. Please see -
On text based elements - Please note that you need to click outside the text box in order to make sure that all the changes are saved on the text element.
Please complete the changes on the text element > Click anywhere on the section outside of the text element box > Make sure the save icon on the top-right side of the screen is shown 'saving' and then 'saved'.
By doing that you ensure that the changes are saved on the text element.