New items\backpacks respawns\erases with time and in case of it new players connects you propose to send for everyone newcomer messages about every loot positions?
Yes, doable in the form of array.asjson . However to set it up, it is not as direct as syncing the position, rather quite tedious but it'll save you bandwidth.
If you don't mind about the bandwidth at all you can still go with syncing positions, but you have to live with the interpolation issue that you show, unless Ashley provide the "no interpolation" option for sync object.
I think the other syncing way you can try is using instance variable. They have no-interpolation mode, so basically record you x and y in the host and have an event in common group to position to instance variable every tick, or every1/30 second depends on what you prefer but the drawback is, the object movement might look choppy, jerky or stuttery.