try flushing the OutputStream at copying on an SD card

build.gradle

@@ -7,7 +7,7 @@ buildscript {
         propMinSdkVersion = 21
         propTargetSdkVersion = propCompileSdkVersion
         propVersionCode = 1
-        propVersionName = '5.15.11'
+        propVersionName = '5.15.13'
         kotlin_version = '1.3.41'
     }
 

commons/src/main/kotlin/com/simplemobiletools/commons/asynctasks/CopyMoveTask.kt

@@ -229,6 +229,8 @@ class CopyMoveTask(val activity: BaseSimpleActivity, val copyOnly: Boolean = fal
                 bytes = inputStream.read(buffer)
             }
 
+            out?.flush()
+
             if (source.size == copiedSize && File(destination.path).exists()) {
                 mTransferredFiles.add(source)
                 if (activity.baseConfig.keepLastModified) {