SSZipArchive sometimes creates corrupt 22 bytes zip file - ios

Question

We are using the SSZipArchive method createZipFileAtPath:withFilesAtPaths: in order to compress a single log file, which is then uploaded to Amazon S3. All files are located in our mobile app's NSTemporaryDirectory().
Sometimes, when I download the resulting zip files from Amazon to my mac and double-click them, I get the following error:
Archive Utility
Unable to expand "[file name].zip" into "[folder name]".
(Error 1 - Operation not permitted.)
When this happens, I always notice that the file size is 22 bytes. This seems too small. When the files behave OK they are usually 1 mb or more.
Here is the relevant code from our app:
-(void) sendConsoleLog
{
//NSError * error;
//NSString * sTemp = [[NSString alloc] initWithContentsOfFile:[self logFilePath] encoding:NSUTF8StringEncoding error:&error];
[SSZipArchive createZipFileAtPath:[self compressedLogFilePath] withFilesAtPaths:#[[self logFilePath]]];
[self upload];
}
-(void) upload
{
_sDestinationFileName = [NSString stringWithFormat:#"logs/%#.zip", [[NSUUID UUID] UUIDString]];
AWSS3TransferUtilityUploadExpression *expression = [AWSS3TransferUtilityUploadExpression new];
expression.progressBlock = self.progressBlock;
[expression setValue:#"public-read" forRequestHeader:#"x-amz-acl"];
AWSS3TransferUtility *transferUtility = [AWSS3TransferUtility defaultS3TransferUtility];
NSString * sFileURL = [NSString stringWithFormat:#"file://%#", [self compressedLogFilePath]];
[[transferUtility uploadFile:[NSURL URLWithString:sFileURL]
bucket:S3_BUCKET_NAME
key:_sDestinationFileName
contentType:#"application/octet-stream"
expression:expression
completionHander:self.completionHandler] continueWithBlock:^id(AWSTask *task) {
if (task.error) {
NSLog(#"cclChatSendLog continueWithBlock Error: %#", task.error);
}
if (task.exception) {
NSLog(#"cclChatSendLog continueWithBlock Exception: %#", task.exception);
}
if (task.result) {
AWSS3TransferUtilityUploadTask *uploadTask = task.result;
NSUInteger iTaskID = uploadTask.taskIdentifier;
NSLog(#"cclChatSendLog.h %lu continueWithBlock: Uploading...", (unsigned long)iTaskID);
}
return nil;
}];
}
-(NSString*) logFilePath
{
NSString *fileName =[NSString stringWithFormat:#"console%lu.log",(unsigned long)(appDelegate.hash)];
return [NSTemporaryDirectory() stringByAppendingPathComponent:fileName];
}
-(NSString*) compressedLogFilePath
{
return [NSString stringWithFormat:#"%#.zip", [self logFilePath]];
}
I wonder if the 22 bytes zip is created in case there is no file found in [self logFilePath]. Has anyone encountered a similar behaviour?