CI Nested Mapgen RNG fail

[Maleclypse]

Describe the bug

([slow] ~starting_items)=>   REQUIRE( msg.empty() )
([slow] ~starting_items)=> with expansion:
Error: ([slow] ~starting_items)=>   false
([slow] ~starting_items)=> with messages:
([slow] ~starting_items)=>   oter_type_id := "office_skyscraper_12"
([slow] ~starting_items)=>   msg := "In nested mapgen skyscraper_office_dr in mapgen office_skyscraper_12
([slow] ~starting_items)=>   on office_skyscraper_12_north, setting terrain to t_linoleum_white (from
([slow] ~starting_items)=>   t_linoleum_gray) at (6,7) when item pencil existed.  Resolve this either by
([slow] ~starting_items)=>   removing the terrain from this mapgen, adding suitable removal commands to
([slow] ~starting_items)=>   the mapgen, or by adding an appropriate clearing flag to the innermost
([slow] ~starting_items)=>   layered mapgen.  Consult the "mapgen flags" section in MAPGEN.md for options.
([slow] ~starting_items)=>   In nested mapgen skyscraper_office_dr in mapgen office_skyscraper_12 on
([slow] ~starting_items)=>   office_skyscraper_12_north, setting terrain to t_linoleum_gray (from
([slow] ~starting_items)=>   t_linoleum_white) at (6,7) when item pencil existed.  Resolve this either by
([slow] ~starting_items)=>   removing the terrain from this mapgen, adding suitable removal commands to
([slow] ~starting_items)=>   the mapgen, or by adding an appropriate clearing flag to the innermost
([slow] ~starting_items)=>   layered mapgen.  Consult the "mapgen flags" section in MAPGEN.md for options.
([slow] ~starting_items)=>   "

Attach save file

NA

Steps to reproduce

Run CI frequently, witness fail states

Expected behavior

Less fail states

Screenshots

No response

Versions and configuration

CI

Additional context

No response