From the V5.2.0 of Layerslider, we noticed a flickering issue with buttons. Any button you place on a slider seems to appear again briefly once it has left, giving the appearance of a flickering.
We found that changing the transition out somewhat fixes this so we suggest it as a workaround.
You can minimise the transition out so that the offending item (button or whatever) so small, that even if the flicker still happens, you can’t really see it.
To do this, on the transition out, scale it to 0 in both the x and y directions. If you can put up with that on your slide it hides the problem sufficiently.