# B2 Error Version Mismatch - Delete Version Fails

**URL:** https://forum.duplicati.com/t/b2-error-version-mismatch-delete-version-fails/9435
**Category:** Support
**Created:** [March 18, 2020, 2:32pm UTC](https://forum.duplicati.com/t/b2-error-version-mismatch-delete-version-fails/9435 "2020-03-18T14:32:35Z")
**Posts on this page:** 1
**Showing post:** 2

<div class="post-metadata">

### Author: ![ts678](https://forum.duplicati.com/letter_avatar_proxy/v4/letter/t/8491ac/32.png) [@ts678](https://forum.duplicati.com/u/ts678)
#### Post date: [March 22, 2020, 2:34pm UTC](https://forum.duplicati.com/t/b2-error-version-mismatch-delete-version-fails/9435/2 "2020-03-22T14:34:59Z")

</div>

> [@shieldedge](#):
>
> I executed a commandline delete with the only option being:  
> –version=75

Does this refer to [Using the Command line tools from within the Graphical User Interface](https://duplicati.readthedocs.io/en/latest/03-using-the-graphical-user-interface/#using-the-command-line-tools-from-within-the-graphical-user-interface)? That’s prepopulated with some essential options plus others you manually added. Don’t delete them all.

Testing my B2 backup, though, deleting --passphrase got a complaint. Keeping that next run then complained about the database (because I deleted --dbpath). I’m not sure how yours timed out…  
My test was on a current Duplicati, and that probably makes some difference in how things work.

There _was_ a [timeout change](https://forum.duplicati.com/t/problems-using-test-filter/6101/9) in January 2019 in web UI’s `Commandline` timeout, which increased allowable time without output from 5 minutes to 24 hours and fixed other things to avoid this error:

> [@Backups fail with error: Object reference not set to an instance of an object](https://forum.duplicati.com/t/backups-fail-with-error-object-reference-not-set-to-an-instance-of-an-object/5570/9):
>
> **Dec 10, 2018 12:13 AM: Failed while executing “Backup” with id: 1** \>System.NullReferenceException: Object reference not set to an instance of an object \> at Duplicati.Library.Utility.FileBackedList`1[T].Add (Duplicati.Library.Utility.T value) \<0x41ee3230 + 0x002a2\> in :0 \> at Duplicati.Server.WebServer.RESTMethods.CommandLine+LogWriter.WriteLine (System.String value) \<0x41f3d0b0 + 0x00123\> in :0 \> at System.IO.TextWriter.WriteLine (System.String format, System.Object arg0, System.Object arg1) \<0x7f23a37d4f10 + 0x0009b\> in :0

which looks similar to the error you had posted.

> [@shieldedge](#):
>
> After getting a file mismatch in a version (75)

Does that refer to “Unexpected difference in fileset”, where the usual repair attempt is version delete?  
The major cause of that was fixed in June 2019 in Canary, and was released in January 2.0.5.1 Beta.  
You should definitely upgrade if you’re getting those, but it won’t fix an existing problem, if you’re in it.

Delete by [Commandline](https://duplicati.readthedocs.io/en/latest/03-using-the-graphical-user-interface/#using-the-command-line-tools-from-within-the-graphical-user-interface) is generally just adding the --version and clearing `Commandline arguments`. Anything you manually added that you suspect is irrelevant can also get deleted. Then run the [delete](https://duplicati.readthedocs.io/en/latest/04-using-duplicati-from-the-command-line/#the-delete-command).  
Sometimes the “Unexpected difference in fileset” moves to a different version, but you’d have to try…

[Backups fail with error: Object reference not set to an instance of an object](https://forum.duplicati.com/t/backups-fail-with-error-object-reference-not-set-to-an-instance-of-an-object/5570/32) was from too few options, however there are probably some other ways to get it. It’s sometimes a follow-up to some other error.

---

_[View the full topic](https://forum.duplicati.com/t/b2-error-version-mismatch-delete-version-fails/9435)._