diff --git a/demo/sat-demo/src/jvmMain/kotlin/ru/mipt/npm/sat/satServer.kt b/demo/sat-demo/src/jvmMain/kotlin/ru/mipt/npm/sat/satServer.kt
index 6ac3e3c2..eea0a4bb 100644
--- a/demo/sat-demo/src/jvmMain/kotlin/ru/mipt/npm/sat/satServer.kt
+++ b/demo/sat-demo/src/jvmMain/kotlin/ru/mipt/npm/sat/satServer.kt
@@ -3,12 +3,19 @@ package ru.mipt.npm.sat
 
 import hep.dataforge.context.Global
 import hep.dataforge.names.asName
+import hep.dataforge.vision.get
 import hep.dataforge.vision.server.visionModule
+import hep.dataforge.vision.solid.Solid
 import hep.dataforge.vision.solid.SolidManager
+import hep.dataforge.vision.solid.color
 import io.ktor.server.cio.CIO
 import io.ktor.server.engine.embeddedServer
 import io.ktor.util.KtorExperimentalAPI
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
 import kotlinx.html.script
+import kotlin.random.Random
 
 @OptIn(KtorExperimentalAPI::class)
 fun main() {
@@ -31,5 +38,13 @@ fun main() {
                 vision("main".asName(), sat)
             }
         }
+        launch {
+            while (isActive){
+                val currentLayer = Random.nextInt(10)
+                (sat["layer[$currentLayer]"] as? Solid)?.color(123)
+                delay(300)
+                (sat["layer[$currentLayer]"] as? Solid)?.color = null
+            }
+        }
     }.start(wait = true)
 }
\ No newline at end of file
diff --git a/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroup.kt b/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroup.kt
index e2101b0c..6fd1c559 100644
--- a/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroup.kt
+++ b/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroup.kt
@@ -97,7 +97,7 @@ public interface MutableVisionGroup : VisionGroup, VisionContainerBuilder<Vision
 //    public operator fun set(name: Name, child: Vision?)
 }
 
-public operator fun <V: Vision> VisionContainer<V>.get(str: String?): V? = get(str?.toName() ?: Name.EMPTY)
+public operator fun <V: Vision> VisionContainer<V>.get(str: String): V? = get(str.toName())
 
 public operator fun <V: Vision>  VisionContainerBuilder<V>.set(token: NameToken, child: V?): Unit = set(token.asName(), child)
 public operator fun <V: Vision>  VisionContainerBuilder<V>.set(key: String, child: V?): Unit = set(key.toName(), child)
diff --git a/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroupBase.kt b/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroupBase.kt
index 767f0e5a..c7fb11c2 100644
--- a/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroupBase.kt
+++ b/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/VisionGroupBase.kt
@@ -15,10 +15,10 @@ public open class VisionGroupBase : VisionBase(), MutableVisionGroup {
 
     /**
      * Internal mutable container for group children
-     * TODO made protected due to https://github.com/Kotlin/kotlinx.serialization/issues/1200
+     * TODO made protected due to [https://github.com/Kotlin/kotlinx.serialization/issues/1200]
      */
     @SerialName("children")
-    protected open val childrenInternal: MutableMap<NameToken, Vision> = LinkedHashMap()
+    protected val childrenInternal: MutableMap<NameToken, Vision> = LinkedHashMap()
 
     /**
      * A map of top level named children
diff --git a/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/visionChange.kt b/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/visionChange.kt
index 76bd6775..9e8b2ad8 100644
--- a/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/visionChange.kt
+++ b/visionforge-core/src/commonMain/kotlin/hep/dataforge/vision/visionChange.kt
@@ -88,15 +88,25 @@ private fun CoroutineScope.collectChange(
     mutex: Mutex,
     target: () -> MutableVisionGroup,
 ) {
-    val targetVision: () -> Vision = { target().getOrCreate(name) }
     //Collect properties change
-    source.onPropertyChange(mutex) { propertyName ->
-        launch {
-            mutex.withLock {
-                targetVision().setProperty(propertyName, source.getProperty(propertyName))
+    source.config.onChange(mutex){propertyName, oldItem, newItem->
+        if(oldItem!= newItem){
+            launch {
+                mutex.withLock {
+                    target().getOrCreate(name).setProperty(propertyName, newItem)
+                }
             }
         }
     }
+//    source.onPropertyChange(mutex) { propertyName ->
+//        launch {
+//            mutex.withLock {
+//                target().getOrCreate(name).setProperty(propertyName, source.getProperty(propertyName,false))
+//            }
+//        }
+//    }
+
+    val targetVision: Vision =  target().getOrCreate(name)
 
     if (source is VisionGroup) {
         check(targetVision is MutableVisionGroup) { "Collector for a group should be a group" }
@@ -124,9 +134,6 @@ private fun CoroutineScope.collectChange(
 
 @DFExperimental
 public fun Vision.flowChanges(scope: CoroutineScope, collectionDuration: Duration): Flow<Vision> = flow {
-    //emit initial visual tree
-    emit(this@flowChanges)
-
     val mutex = Mutex()
 
     var collector = VisionGroupBase()
diff --git a/visionforge-server/src/main/kotlin/hep/dataforge/vision/server/VisionServer.kt b/visionforge-server/src/main/kotlin/hep/dataforge/vision/server/VisionServer.kt
index 8b53dc90..5ea07639 100644
--- a/visionforge-server/src/main/kotlin/hep/dataforge/vision/server/VisionServer.kt
+++ b/visionforge-server/src/main/kotlin/hep/dataforge/vision/server/VisionServer.kt
@@ -29,6 +29,7 @@ import io.ktor.routing.get
 import io.ktor.routing.route
 import io.ktor.routing.routing
 import io.ktor.server.engine.ApplicationEngine
+import io.ktor.util.error
 import io.ktor.websocket.WebSockets
 import io.ktor.websocket.webSocket
 import kotlinx.coroutines.flow.collect
@@ -129,8 +130,9 @@ public class VisionServer internal constructor(
                                 val json = visionManager.encodeToString(update)
                                 outgoing.send(Frame.Text(json))
                             }
-                        } catch (ex: Exception) {
-                            application.log.debug("Closed server socket for $name with exception $ex")
+                        } catch (ex: Throwable) {
+                            application.log.error("Closed server socket for $name with exception $ex")
+                            application.log.error(ex)
                         }
                     }
                     //Plots in their json representation