I'd like to ask some questions about the latest experimental version of debug

DEBUG : (json-error)
Json error: storage/emulated/0/Android/data/com.cleverraven.cataclysmdda.experimental/files/data/mods/Kenan-Modpack-Chinese/secronom/Modification_Files/Monsters/-Essentials/secro_ammo_zombie.json:26:25: Invalid or misplaced field name “countdown_destroy” in JSON data

"explode_in_fire": true,
"countdown_interval": 1,
"countdown_destroy":
                    ^
                     true,
"countdown_action": { "target": "SSxgrenadeact", "target_charges": 10, "active": true, "type": "transform" }

},

FUNCTION : void JsonObject::error_skipped_members(const std::vector<size_t> &) const
FILE : /home/runner/work/Cataclysm-DDA/Cataclysm-DDA/android/app/jni/src/…/…/…/…/src/flexbuffer_json.cpp
LINE : 333
VERSION : 720adec

I would like to ask how I should solve such debug, I looked through the txt, it seems to be no problem, but after running the game, there will be this debug, I am very confused.

As a general rule and good practice, I highly suggest to always include the exact version build ID, as what’s considered “last experimental” or “current experimental” changes every few hours, and might even be different depending on where you’ve grabbed it from.
Aside from the version, you also should always add your operating system and the mods you’re using, as they can make a big difference.

Now as for this specific case and to answer your question to the best of my ability, take a closer look at what the debug message says:

This tells you that the game doesn’t understand/accept "countdown_destroy" on this item.
The reason is this pull request, which removed the processing of "countdown_destroy" from the game.

As a possible solution I suggest to delete all occurrences of "countdown_destroy": true, from the mod files.