Milestone 1 throws errors in latest experimental

[bcmcms]

Attempting to load a sky islands game on the current experimental version (2024-01-26-1600) after replacing the Sky Island mod files with the latest from the repo gives the following error:

DEBUG : Error: Json error: data/mods/Sky_Island/EOCs.json:421:87: <color_white><color_cyan>unrecognized number source in { "time": "15 m" }

    "u_message": "All difficulty settings set to default.  You can speak to the Heart of the Island to change these at any time."

},
<color_light_red> { "arithmetic": [ { "global_val": "var", "var_name": "sicknessintervals" }, "=", { "time": "15 m" } ] },

<color_cyan>▲▲▲
{ "math": [ "roomteleportselector", "=", "1" ] },
{ "math": [ "u_spell_level('warp_home')", "=", "-1" ] },

FUNCTION : load_game
FILE : D:\a\Cataclysm-DDA\Cataclysm-DDA\src\main_menu.cpp
LINE : 1038
VERSION : 0f39e72

Attempting to start a new game gives many errors of the form

DEBUG : (json-error)
Json error: data/json/artifact/artifact_item_types.json:223:17: <color_white><color_cyan>Invalid or misplaced field name "copy-from" in JSON data

"id": "art_robe",
"type": "ARMOR",

<color_light_red> "copy-from": "robe",

<color_cyan>▲▲▲
"name": { "str": "royal robe" },
"description": "An ornately decorated robe with an unfamiliar royal symbol on it. The humanoid figure on the seal has two pairs of eyes. It is the only one of its kind.\nIt may have unknown powers; try activating them."

FUNCTION : error_skipped_members
FILE : D:\a\Cataclysm-DDA\Cataclysm-DDA\src\flexbuffer_json.cpp
LINE : 347
VERSION : 0f39e72

[bcmcms]

Info from Discord seems to suggest this is related to this: CleverRaven/Cataclysm-DDA#70996