are you still using html buttons, or did you switch to making buttons from sprites and text objects?
html buttons are not part of the canvas, and getting rid of the lag is pretty complicated. ROJOhound found a solution a year or so ago, but I would have to do some searching to find it.
if you are using sprites/text, then everything must be pinned to the same moving object. If you have a panel that slides in, and buttons pinned to that, and text pinned to the buttons, then the text will lag behind. The text should also be pinned to the panel.
make a small test file with sample buttons so we can see what is going on.