Object paging causes gradual performance deteriation in exteriors

When object paging is enabled, an unaccountable gap begins to appear in the frame graph as the player travels and more objects are paged. This is easily and quickly reproducible by traveling around the map at high speed in a single session, especially areas dense with objects added by the various province mods (TR, PT, etc.) The effect is increased when active grid paging is enabled. This gap doesn't occur if object paging is disabled.

coe -3 -4 Before/after traveling around the map:

And a comparison with object paging disabled, with no gap:

(Note that even this also leads to longer frame times generally, which itself may be an example of #5707 and its related issues.)