Content.json write error: false This file still in sync [SKIPPED] content.json

### Step 1: Please describe your environment

* ZeroNet version: 4455
* Operating system: W10
* Web browser: FF beta

### Step 2: Describe the problem:

Hello, suddenly when i tried to publish changes on my zeroblog clone, it shown on site error:

> Content.json write error: false

and prompt:

> This file still in sync, if you write it now, then the previous content may be lost. [ Write content anyway ]

in debug log is:

> INFO Site:1abc..def Opening site data directory: C:/ZeroNet-win-dist-win64/data/1abc...def/...
> INFO Site:1abc..def - [SKIPPED] content.json

same for:
"[SKIPPED] data/users/content.json"
"[SKIPPED] data/data.json-old"

> INFO Site:1abc..def Signing content.json...
> INFO Site:1abc..def Saving to content.json...
> INFO Site:1abc..def File content.json signed!

then i reload the site (F5) and after two hours without restarting or updating Zeronet, the publishing on that site works again without any messages mentioned above.

HDD has enough disk space. Though my RAM was exhausted.

Maybe you have clue what can cause this. If no and i can do something to discover more details, let me know and i will provide it.