Travelers backpack somehow takes over gravestone if they are loaded at the same time. Gravestone wont spawn graves and wont put the config in the world/serverconfig even after travelers is removed
although, strangely it will recreate the travelers config in .minecraft/config after removing travelers mod and travelers config instead of gravestone config . But if they (the mods) are both removed and then gravestone is loaded into a world first and then travelers, it all works fine so far.
debug.log
latest.log

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So, I tested it, and it works perfectly fine. If you die with the backpack on, it just spawns next to the gravestone.

Please try a clean install of your minecraft instance and report this issue again (Please fill out the bug template next time) if it still doesn't work.