Possible bug in MQTT Block (Simulink, MATLAB R2025b) – Password disappears after Apply

Hey everyone,

I’m currently working with MATLAB R2025b and using the MQTT blocks from the Industrial Communication Toolbox inside Simulink. I’ve run into an issue that’s driving me a bit crazy, and I’m not sure if it’s a bug or if I’m missing something obvious.

Here’s what’s happening:

• I open the MQTT Configure block.
• I fill out all the required fields — Broker address, Port, Client ID, Username, and Password.
• When I click Test Connection, it says “Connection established successfully.” So far so good.
• Then I click Apply, close the dialog, set the topic name, and try to run the simulation.
• At this point, I get the following error:Caused by: Invalid value for 'ClientID', 'Username' or 'Password'.
• When I reopen the MQTT config block, I notice that the Password field is empty again — even though I definitely entered it before and the connection test worked earlier.

It seems like Simulink is somehow not saving the password after hitting Apply, which leads to the authentication error during simulation.

Has anyone else faced this? Is this a bug in R2025b, or do I need to configure something differently to make the password persist?

Would really appreciate any insights, workarounds, or confirmations from anyone who has used MQTT in Simulink recently.

Thanks in advance!