Its normal, after the main destruction of nearly all foundation that were build at same time (in connection), if it remain just some islolated foundations it break their old decay time that was matching the network of foundations to replace it by the decay timer of one foundation only, so something like 40mn.
@@darksh1ne1 yup, but that only works when only very few foundations left and space by something like 3-4 square between isolated foundation. so well hard to acheive, especially for cave base. so congrats.