diff --git a/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupImportService.java b/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupImportService.java
index 9380079..65211de 100644
--- a/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupImportService.java
+++ b/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupImportService.java
@@ -1,5 +1,6 @@
 package de.ph87.homeautomation.knx.group;
 
+import de.ph87.homeautomation.property.PropertyReader;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
 import org.jsoup.Jsoup;
@@ -23,6 +24,8 @@ public class KnxGroupImportService {
 
   private final KnxGroupRepository knxGroupRepository;
 
+  private final PropertyReader propertyReader;
+
   public void importGroups() {
     try {
       execute("/usr/bin/git", "fetch", "--all");
@@ -34,6 +37,18 @@ public class KnxGroupImportService {
     knxGroupRepository.findAll().forEach(knxGroup -> knxGroup.setEts(false));
     try {
       Jsoup.parse(new File(ETS_HOME, "G"), "UTF-8").select("GA").forEach(this::importGroup);
+      knxGroupRepository.findAllByEtsFalse().forEach(group -> {
+        log.warn("Removing obsolete group: {}", group);
+        propertyReader.findAllByReadChannel_Id(group.getId()).forEach(property -> {
+          property.setReadChannel(null);
+          log.warn("  - removed group as Property readChannel: {}", property);
+        });
+        propertyReader.findAllByWriteChannel_Id(group.getId()).forEach(property -> {
+          property.setWriteChannel(null);
+          log.warn("  - removed group as Property writeChannel: {}", property);
+        });
+        knxGroupRepository.delete(group);
+      });
     } catch (IOException e) {
       log.error("Failed to import KnxGroups: {}", e.toString());
     }
@@ -73,7 +88,13 @@ public class KnxGroupImportService {
   private void setDpt(final KnxGroup knxGroup, final String dptString) {
     final Matcher mainSub = Pattern.compile("^DPST-(?<main>\\d+)-(?<sub>\\d+)$").matcher(dptString);
     if (mainSub.matches()) {
-      knxGroup.setDptMain(Integer.parseInt(mainSub.group("main")));
+      final int main = Integer.parseInt(mainSub.group("main"));
+      if (knxGroup.getDptMain() != main) {
+        knxGroup.setLastTelegram(null);
+        knxGroup.setValue(null);
+        knxGroup.setTimestamp(null);
+      }
+      knxGroup.setDptMain(main);
       knxGroup.setDptSub(Integer.parseInt(mainSub.group("sub")));
       return;
     }
diff --git a/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupRepository.java b/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupRepository.java
index 72c689d..b6e8bb1 100644
--- a/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupRepository.java
+++ b/src/main/java/de/ph87/homeautomation/knx/group/KnxGroupRepository.java
@@ -1,18 +1,16 @@
 package de.ph87.homeautomation.knx.group;
 
 import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
-import org.springframework.data.repository.CrudRepository;
+import org.springframework.data.repository.ListCrudRepository;
 
 import java.time.ZonedDateTime;
 import java.util.List;
 import java.util.Optional;
 
-public interface KnxGroupRepository extends CrudRepository<KnxGroup, Long>, JpaSpecificationExecutor<KnxGroup> {
+public interface KnxGroupRepository extends ListCrudRepository<KnxGroup, Long>, JpaSpecificationExecutor<KnxGroup> {
 
   Optional<KnxGroup> findByAddressRaw(int rawAddress);
 
-  List<KnxGroup> findAll();
-
   Optional<KnxGroup> findFirstBySend_NextTimestampNotNullOrderBySend_NextTimestampAsc();
 
   Optional<KnxGroup> findFirstByRead_NextTimestampLessThanEqualOrderByRead_NextTimestampAsc(ZonedDateTime timestamp);
@@ -21,4 +19,6 @@ public interface KnxGroupRepository extends CrudRepository<KnxGroup, Long>, JpaS
 
   List<KnxGroup> findAllByNameContainsIgnoreCaseOrAddressStrContainsIgnoreCase(String name, String addressStr);
 
+  List<KnxGroup> findAllByEtsFalse();
+
 }
diff --git a/src/main/java/de/ph87/homeautomation/property/PropertyReader.java b/src/main/java/de/ph87/homeautomation/property/PropertyReader.java
index f03a15b..6ad32e3 100644
--- a/src/main/java/de/ph87/homeautomation/property/PropertyReader.java
+++ b/src/main/java/de/ph87/homeautomation/property/PropertyReader.java
@@ -23,6 +23,10 @@ public class PropertyReader {
     return propertyRepository.findAllByReadChannel_Id(readChannelId);
   }
 
+  public List<Property> findAllByWriteChannel_Id(final long writeChannelId) {
+    return propertyRepository.findAllByWriteChannel_Id(writeChannelId);
+  }
+
   public List<PropertyDto> search(final String term) {
     return RepositorySearchHelper.search(term, propertyRepository, "title", propertyMapper::toDto);
   }
diff --git a/src/main/java/de/ph87/homeautomation/property/PropertyRepository.java b/src/main/java/de/ph87/homeautomation/property/PropertyRepository.java
index 38caa23..6bd5987 100644
--- a/src/main/java/de/ph87/homeautomation/property/PropertyRepository.java
+++ b/src/main/java/de/ph87/homeautomation/property/PropertyRepository.java
@@ -12,7 +12,7 @@ public interface PropertyRepository extends JpaRepository<Property, Long>, JpaSp
 
   List<Property> findAllByReadChannel_Id(long readChannelId);
 
-  List<Property> findAllByTitleLikeIgnoreCase(final String like);
+  List<Property> findAllByWriteChannel_Id(final long writeChannelId);
 
   boolean existsByTitle(String title);