While Davdroid usually works flawlessly, I experience a crash when synchronising the contacts after installing Linphone on my Phone.
I think it might be related to the fact that Linphone somehow creates a connection to existing contacts that are being synced via Davdroid and adds sip-addresses which somehow lead to a crash when Davdroid tries to do the synchronisation. If I uninstall Linphone, remove the Davdroid account and create the Davdroid account with the same URL again, it works again (until I install Linpone again).
Here a few details:
Phone: OnePlus One with CyanogenOS (Andrdoid 4.4.4)
Davdroid 0.7.7
Carddav-Server: Owncloud 8.0.3
Debug log (I think this is the relevant part)
I/davdroid.DavSyncAdapter(26412): Performing sync for authority com.android.contacts
D/davdroid.DavSyncAdapter(26412): Creating new DavHttpClientV/davdroid.TlsSniSocketFactory(26412): Setting allowed TLS protocols: TLSv1, TLSv1.1, TLSv1.2
V/davdroid.TlsSniSocketFactory(26412): Setting allowed TLS ciphers: TLS_ECDH_RSA_WITH_3DES_EDE_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, TLS_DHE_RSA_WITH_AES_128_CBC_SHA, TLS_ECDH_RSA_WITH_AES_128_CBC_SHA, TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA, SSL_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA, SSL_RSA_EXPORT_WITH_RC4_40_MD5, TLS_DHE_RSA_WITH_AES_256_CBC_SHA, SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA, TLS_ECDH_RSA_WITH_AES_256_CBC_SHA, SSL_RSA_WITH_RC4_128_SHA, TLS_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA, SSL_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA, TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, SSL_DHE_DSS_WITH_DES_CBC_SHA, TLS_ECDHE_RSA_WITH_RC4_128_SHA, TLS_ECDH_ECDSA_WITH_RC4_128_SHA, TLS_DHE_DSS_WITH_AES_256_CBC_SHA, TLS_RSA_WITH_AES_128_CBC_SHA, SSL_DHE_RSA_WITH_DES_CBC_SHA, TLS_ECDHE_ECDSA_WITH_RC4_128_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA, TLS_RSA_WITH_AES_256_CBC_SHA, SSL_RSA_WITH_DES_CBC_SHA, TLS_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA,
TLS_ECDH_RSA_WITH_RC4_128_SHA, TLS_EMPTY_RENEGOTIATION_INFO_SCSV, SSL_RSA_EXPORT_WITH_DES40_CBC_SHA, TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA, SSL_RSA_WITH_RC4_128_MD5, TLS_DHE_DSS_WITH_AES_128_CBC_SHA, SSL_DHE_DSS_WITH_3DES_EDE_CBC_SHA, SSL_RSA_WITH_3DES_EDE_CBC_SHA
D/davdroid.DavSyncAdapter(26412): Server supports VCard version 3.0
V/davdroid.URIUtils(26412): Normalized URL XXX_REMOVED_XXX
D/davdroid.WebDavResource(26412): Using preemptive authentication (not compatible with Digest auth)
I/davdroid.SyncManager(26412): Remotely removing 0 deleted resource(s) (if not changed)
I/davdroid.SyncManager(26412): Uploading 0 new resource(s) (if not existing)
I/davdroid.SyncManager(26412): Uploading 1 modified resource(s) (if not changed)
D/davdroid.resource(26412): Populating group from sourceid=? AND deleted=0 XXX_REMOVED_XXX
D/davdroid.resource(26412): Populating group from sourceid=? AND deleted=0 XXX_REMOVED_XXX
D/davdroid.DavSyncAdapter(26412): Closing httpClient
E/AndroidRuntime(26412): FATAL EXCEPTION: SyncAdapterThread-1
E/AndroidRuntime(26412): Process: at.bitfire.davdroid:sync, PID: 26412
E/AndroidRuntime(26412): java.lang.NullPointerException
E/AndroidRuntime(26412): at at.bitfire.davdroid.resource.LocalAddressBook.populateSipAddress(LocalAddressBook.java:635)
E/AndroidRuntime(26412): at at.bitfire.davdroid.resource.LocalAddressBook.populate(LocalAddressBook.java:251)
E/AndroidRuntime(26412): at at.bitfire.davdroid.resource.LocalCollection.findById(LocalCollection.java:210)
E/AndroidRuntime(26412): at at.bitfire.davdroid.syncadapter.SyncManager.pushDirty(SyncManager.java:168)
E/AndroidRuntime(26412): at at.bitfire.davdroid.syncadapter.SyncManager.synchronize(SyncManager.java:50)
E/AndroidRuntime(26412): at at.bitfire.davdroid.syncadapter.DavSyncAdapter.onPerformSync(DavSyncAdapter.java:146)E/AndroidRuntime(26412): at android.content.AbstractThreadedSyncAdapter$SyncThread.run(AbstractThreadedSyncAdapter.java:259)