Yep, this is an issue. Had to deal with it yesterday and it requires some JS to manually set the tab index. The issue is that Bubble draws the html elements in the order they are created (not the order displayed) and simply uses the flexbox order property to reposition the elements on the page.
As you can see from the attached gif, while the inputs I have on the page visually go
First name
Last name
Email
Password
In the html they are drawn as
First name
Password
Email
Last name
Since no tab order is set on the inputs the browser has to anticipate which input should be next and is using the html structure to do that.