Extreme Lag spikes when updating old world to 1.18

When updating an old World to 1.18 I experienced extreme lag spikes. Especially in chunks first created at version 1.5.2. 

Lags occurred when trying to view new caved in spectator mode.

In newer chunks (1.15 generated) there were some lags, But in the old chunks (1.5.2 generated) there were severy lag spikes that kept on going for multiple minutes until I left the cave systems. (Simulation distance: 5 Render Distance 14)