Cheese or toppings slide off before baking (while topping or launching)

Cosmetic

A pre-bake handling and adhesion issue, distinct from toppings sliding off when slicing after baking.

Ask yourself

Is this happening before the pizza goes in the oven, rather than when slicing afterward?
How much bench flour or semolina is on the dough's surface under the sauce?
Was the dough surface tacky enough for the sauce and cheese to grip, or dry and slick?

#1
Excess bench flour or semolina left on the dough's surface, creating a dry, low-grip layer under the sauce
Strongly supported
The same dusting flour that stops dough sticking to the peel also stops toppings gripping the dough if too much is left on top rather than shaken off underneath.
#2
Too little sauce or oil to act as an adhesive layer between the dough and the cheese
Generally accepted
Cheese needs some moisture or fat underneath it to bind to the dough surface before baking sets it in place.
#3
Aggressive movement while topping, launching, or transporting the pizza to the oven
Generally accepted
Toppings that aren't yet bonded to the dough can shift or fall during a jerky launch or an uneven carry to the oven.

Gently reposition displaced toppings before the pizza goes in, or immediately after launching while the surface is still soft

Shake off excess bench flour before topping, use a thin even layer of sauce or oil for grip, and handle the assembled pizza smoothly and confidently

Guides that treat this as an outcome to improve, an environment to work with, or a flavour to understand, rather than only a problem to fix.