Hi ​@maphril_GBL 

Can you create a minimalist shape library containing only one or two basic shapes.

Export the library and then immediately attempt to re-import it.

This test will help determine if the problem is isolated to the original library or if it's a broader issue with all .lcsl files.

Best Regards

Hi ​@maphril_GBL, thank you for posting your question in the Lucid Community, I’m happy to provide additional help! I would recommend reading the Shape libraries in Lucidchart article from the Lucid Help Center to get an understand of this functionality. 

First, a few troubleshooting steps to begin:

1.  The troubleshooting step that ​@Humas1985 suggested may help in determining whether this issue is consistent. Does this issue occur across multiple shape libraries and documents, or just the one? 

2. Could you try opening your document in a private or incognito window to help us narrow down the potential cause? For help with opening an incognito window, please see this community post.
3. Could you also try connecting to a different network or disconnecting from your VPN (if applicable)? Sometimes the error message you are receiving can be related to internet security/speed or browser issues. These steps will help us eliminate that possibility. 

Can you confirm whether the above steps helped to resolve this? If the issue persists, can you please send the following information so I can take a closer look?

• A screenshot of the associated Javascript Console output after reproducing the issue. You can open your Javascript Console by pressing Ctrl+Shift+J (if your computer is a Windows/Linux) OR Cmd+Opt+J (if your computer is a Mac).

Another option here:

If you are on a Team or Enterprise account, you can share your custom shape libraries with other Team and Enterprise account users. You can use this method to share your shape library with the other account. 

Here’s how:

1. Click More shapes at the bottom of the Shape menu.
2. Expand the “My libraries” dropdown in the left-side panel.
3. Select the custom library you want to share.
4. Click Share in the upper-right corner.
5. In the share window that appears, add collaborators by name or email address.
6. Select Invite.

Thank you for your help and patience as I look into this issue!