The content length was changed from the default 300,000 to 1,000,000.

<content_length>
<default>1000000</default>
</content_length>

The session_timeout_millis was changed from the default 5000 to 60000.

<session_timeout_millis>60000</session_timeout_millis>

We do push a lot of data to the client. The client CPU load is often quite high, sometimes 80% of CPU usage.

Unfortunately, I don't have more info about the JS exception.