[Bug] Null characters inserted on backup to CIFS provider

[billfor]

Guidelines

• I have read the FAQ and it doesn't cover the issue.
• I have searched the issue tracker for open and closed issues that are similar to the feature request I want to file, without success.
• I'm on the latest version.
• I'm not using a test build (alpha/beta/release-candidate).
• This issue contains only one bug.

Describe the bug

I'm on the March 2026 Android release and I have a strange problem when using Neo-Backup via the CIFS provider. I have not used Neo-Backup in a year but in the past I had no issues. I am using the current version and also tried the last two versions.

If I back up all the apps at once, the files(s) seem to have extra NULL characters added, which makes the backup invalid and not recognized for recovery. This only happens if I try to backup everything (so that multiple operations are running in parallel) and not if I go into each app separately and do a backup.

For example, adobe reader backed up in a batch operation with many others, vs just backing it up by clicking into it and selecting backup:

Administrator@Ratbert3 MINGW64 //qnap/Test/backup/com.adobe.reader
$ ls
2026-03-17-13-08-13-585-user_0/  2026-03-17-13-08-13-585-user_0.properties  2026-03-18-00-12-22-387-user_0/  2026-03-18-00-12-22-387-user_0.properties

The 3/17 is from a batch with 100 other apps, and 3/18 is done separate. If we look at 2026-03-17-13-08-13-585-user_0.properties or bring it into an editor, we see it padded with 4 NULLs. As a result, this will not appear as a valid backup to select as a restore (the backup is ignored).

$ tail -c 16 2026-03-17-13-08-13-585-user_0.properties | od -A n -t c -t x1
       1   4   6   4   2   4   5   7   6  \n   }  \0  \0  \0  \0
  20  31  34  36  34  32  34  35  37  36  0a  7d  00  00  00  00

When processing a batch of 100 or more apps, not every app turns out like this, but most do. If I manually remove these nulls and rewrite the prop file, then I can see the file for restore in Neo-Backup, however if will fail with other errors (invalid apk) probably because the apk's themselves have NULLs at the end.

adobe.tar.gz

Expected Behavior

Looking for valid files so I can restore. Since this used to work a long time ago for me, and since it always works for any app if I do each one manually, I wonder if some type of paralleling is causing the issue. I don't think it's the CIFS provider off hand -- I can actually make a local backup on my pixel, and then copy if over and everything works (no NULLs).
One thing that might come in handy is a way to slow things down and run in single-threaded mode so only one app is backed up at a time - maybe that would work better since I can always do a backup manually by drilling into each application and clicking the backup button, and that always works. Single threaded backup could also come in handy when backing up to a USB OTG drive - I've noticed that multiple i/o operations really hammer the drive and it takes a long time.

Neo Backup's Version

8.3.17, 8.3.16, and 8.3.15

Installation Source

Official F-Droid repo

Last Known Working Version

can't remember

Relevant information

• Device: Pixel 8
• Android Version: 16 March 2026 QPR
• ROM: stock