---
title: "Known issues"
url: "https://help.dectris.cloud/en/article/known-issues"
language: "en"
last_updated: "2026-07-15T08:53:37.451Z"
---

# Known issues

This page lists known issues in **DECTRIS D.LAB**, along with recommended workarounds. We actively monitor these issues and update this page as improvements are made.

## **VPN Can Block Session Connection**

**Issue**

Some VPN configurations can prevent a successful connection to your DECTRIS D.LAB session.

**Symptoms**

-   After starting a session, it is not possible to connect to the session at all. The session tab shows the error "Connection Closed"![](https://cdn-assets.productfruits.com/4c4c7555-40c7-42a3-8d5b-f8c56e56a934)

**Workaround**

-   Disconnect from your VPN and try connecting again
-   Make sure you have not opened the session tab several times

## **Session Crashes Due to Memory Limits**

**Issue**  
If a session exceeds its available memory, it may crash and become unreachable.

**Symptoms**

-   Session suddenly disconnects with the error message "Transport error":![](https://cdn-assets.productfruits.com/6eb1035b-3969-4c31-a4d5-f8801bb660b2)
-   When closing the tab and trying to start the session again, you get an error message "504 Gateway Time-out":![](https://cdn-assets.productfruits.com/2af0837b-2ab3-4cf7-9df2-9891dd13a29f)
-   Session appears to be running but cannot be accessed

**Workaround**

-   Stop the session and start the session again
-   If you repeatedly encounter memory issues, start a new session with more RAM

> Note: Any unsaved work in the session will be lost when the session crashes.

## **Persistent Black Screen After Session Start**

**Issue**  
In rare cases, a session may start but only display a black screen, even while waiting a long time after session start.

**Symptoms**

-   Session starts successfully and goes into a running state.
-   Browser window shows a black or blank screen

**Workaround**

-   Stop the session and start the session again

## **Project or Experiment Folders Become Unmounted Inside of Session**

**Issue**  
Project or experiment folders mounted under the `/dectris_data` path can unexpectedly become inaccessible during a session.

This can occur after encountering the error message **“Transport endpoint is not connected”**, which indicates a problem with the underlying file system mount.

**Symptoms**

-   Folders under `/dectris_data` are no longer accessible
-   File operations fail (e.g. listing, reading, or writing files)
-   Error message: *Transport endpoint is not connected*

**Workaround**

-   Stop the session and start it again to re-mount the folders

**If the issue persists**

-   If the folders are still not accessible after restarting the session, contact DECTRIS support at [**support@dectris.cloud**](https://)
-   Include the **session ID**, if possible, to help with troubleshooting