placement: handle existing block edge case

src/ReplicatedStorage/Shared/PlacementManager.lua

@@ -31,6 +31,7 @@ local lastNormalId: Enum.NormalId? = nil
 local lastRaycastFailure: string? = nil
 local lastSelectedChunkKey: string? = nil
 local lastSelectedBlockKey: string? = nil
+local duplicateResyncCooldown: {[string]: number} = {}
 local BREAK_ROLLBACK_TIMEOUT = 0.6
 local pendingBreaks = {}
 local clearSelection
@@ -426,14 +427,14 @@ function PlacementManager:PlaceBlock(cx, cy, cz, x, y, z, blockId: string)
 		return
 	end
 
-	-- if the client already thinks this block is the same id, skip sending
+	-- allow sending even if the client thinks the id matches; server truth wins
 	if chunk then
 		local existing = chunk:GetBlockAt(x, y, z)
 		local existingId = existing and existing.id
 		if existingId and tostring(existingId) == tostring(blockId) then
 			debugPlacementLog(
-				"[PLACE][CLIENT][SKIP]",
+				"[PLACE][CLIENT][DUPLICATE]",
-				"duplicate id",
+				"still sending",
 				"chunk",
 				cx,
 				cy,
@@ -447,7 +448,14 @@ function PlacementManager:PlaceBlock(cx, cy, cz, x, y, z, blockId: string)
 				"blockId",
 				blockId
 			)
-			return
+			local ck = makeChunkKey(cx, cy, cz)
+			local last = duplicateResyncCooldown[ck]
+			if not last or (tick() - last) > 0.5 then
+				duplicateResyncCooldown[ck] = tick()
+				task.defer(function()
+					ChunkManager:RefreshChunk(cx, cy, cz)
+				end)
+			end
 		else
 			debugPlacementLog(
 				"[PLACE][CLIENT][EXISTING]",

src/ServerScriptService/Actor/ServerChunkManager/init.server.lua

@@ -138,7 +138,7 @@ local function isBlockInsidePlayer(blockPos: Vector3): boolean
 	return false
 end
 
-local DEBUG_PLACEMENT = true
+local DEBUG_PLACEMENT = false
 local function debugPlacementLog(...: any)
 	if DEBUG_PLACEMENT then
 		Util.StudioLog(...)