Configuration dialogs for legacy UI nodes stop working after first use in KNIME 5.12.0 LTS

Hello KNIME Community,

we are currently experiencing a major technical issue with our KNIME Analytics Platform, currently running version 5.12.0 LTS.

The issue affects nodes that still use the legacy configuration dialog instead of the new configuration sidebar on the right-hand side, for example GroupBy, JSON Path, and similar nodes.

The behavior is as follows:

• After completely restarting KNIME, we can open and configure these nodes normally.

• After closing the configuration dialog for the first time, we are no longer able to properly reopen or modify the configuration.

• If we need to make any further adjustments, we have to close and restart KNIME completely.

• After restarting, the configuration dialog works again, but only once. The same issue then occurs again.

This makes working with these nodes very difficult, especially when configurations need to be adjusted or tested repeatedly.

We have been experiencing this issue since July, and unfortunately, several KNIME updates have not resolved it.

Has anyone experienced similar behavior, or is this a known issue?
We would greatly appreciate any advice on how to troubleshoot or resolve this. If additional technical information, logs, or system details are required, we would be happy to provide them.

Thank you very much in advance for your support!

Best regards,
Marcus