diff --git a/opencloudApp/src/main/java/eu/opencloud/android/workers/UploadFileFromContentUriWorker.kt b/opencloudApp/src/main/java/eu/opencloud/android/workers/UploadFileFromContentUriWorker.kt
index bee2f350d..42f7eadee 100644
--- a/opencloudApp/src/main/java/eu/opencloud/android/workers/UploadFileFromContentUriWorker.kt
+++ b/opencloudApp/src/main/java/eu/opencloud/android/workers/UploadFileFromContentUriWorker.kt
@@ -50,7 +50,6 @@ import eu.opencloud.android.domain.transfers.TransferRepository
 import eu.opencloud.android.domain.transfers.model.OCTransfer
 import eu.opencloud.android.domain.transfers.model.TransferResult
 import eu.opencloud.android.domain.transfers.model.TransferStatus
-import eu.opencloud.android.extensions.isContentUri
 import eu.opencloud.android.extensions.parseError
 import eu.opencloud.android.domain.capabilities.usecases.GetStoredCapabilitiesUseCase
 import eu.opencloud.android.lib.common.OpenCloudAccount
@@ -140,9 +139,20 @@ class UploadFileFromContentUriWorker(
             getWebdavUrlForSpaceUseCase(GetWebDavUrlForSpaceUseCase.Params(accountName = account.name, spaceId = ocTransfer.spaceId))
 
         val localStorageProvider: LocalStorageProvider by inject()
-        cachePath = localStorageProvider.getTemporalPath(account.name, ocTransfer.spaceId) + uploadPath
-
-        if (ocTransfer.isContentUri(appContext)) {
+        // Prepend uploadId to the cache filename so two transfers targeting the same
+        // uploadPath (e.g. same filename in two different SAF source folders) can't collide
+        // on the same cache file and PUT each other's bytes (issue #78). Flat layout — no
+        // nested subdirs to clean up, original filename and extension preserved for debugging.
+        val flatCacheName = "${uploadIdInStorageManager}_" + File(uploadPath).name
+        cachePath = localStorageProvider.getTemporalPath(account.name, ocTransfer.spaceId) +
+                File.separator + flatCacheName
+
+        // Re-copy if the cache file is missing or empty. A previous run may have copied it
+        // and then had it removed (e.g. by removeCacheFile() at the end of a successful run
+        // that the OS killed before bookkeeping). Only the contentUri from worker params is
+        // authoritative.
+        val cacheFile = File(cachePath)
+        if (!cacheFile.exists() || cacheFile.length() == 0L) {
             checkDocumentFileExists()
             checkPermissionsToReadDocumentAreGranted()
             copyFileToLocalStorage()
diff --git a/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/common/network/FileRequestBody.kt b/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/common/network/FileRequestBody.kt
index 5290e2601..9e2df7420 100644
--- a/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/common/network/FileRequestBody.kt
+++ b/opencloudComLibrary/src/main/java/eu/opencloud/android/lib/common/network/FileRequestBody.kt
@@ -51,26 +51,24 @@ open class FileRequestBody(
     override fun contentLength(): Long = file.length()
 
     override fun writeTo(sink: BufferedSink) {
-        val source: Source
-        var it: Iterator<OnDatatransferProgressListener>
-        try {
-            source = file.source()
-            var transferred: Long = 0
-            var read: Long
-            while (source.read(sink.buffer, BYTES_TO_READ).also { read = it } != -1L) {
+        // Don't swallow IO errors here — a missing source file used to silently produce
+        // a 0-byte PUT that the server happily stored (issue #78).
+        val source: Source = file.source()
+        var transferred: Long = 0
+        var read: Long
+        source.use { src ->
+            while (src.read(sink.buffer, BYTES_TO_READ).also { read = it } != -1L) {
                 transferred += read
                 sink.flush()
                 synchronized(dataTransferListeners) {
-                    it = dataTransferListeners.iterator()
+                    val it = dataTransferListeners.iterator()
                     while (it.hasNext()) {
                         it.next().onTransferProgress(read, transferred, file.length(), file.absolutePath)
                     }
                 }
             }
-            Timber.d("File with name ${file.name} and size ${file.length()} written in request body")
-        } catch (e: Exception) {
-            Timber.e(e)
         }
+        Timber.d("File with name ${file.name} and size ${file.length()} written in request body")
     }
 
     override fun addDatatransferProgressListener(listener: OnDatatransferProgressListener) {