Lightning strikes are randomized server- and client-side, while they should only be randomized server-side. This can result in too long or too short lightning strikes client-side. For example the player is not seeing lightning bolts anymore but is still damaged.
Based on 1.11.2 decompiled using MCP 9.35 rc1
The constructor net.minecraft.entity.effect.EntityLightningBolt.EntityLightningBolt(World, double, double, double, boolean) chooses the life time client-side and the method net.minecraft.entity.effect.EntityLightningBolt.onUpdate() randomizes how long the lightning strike will take.