[#3986] PHP warning on line 3559

krileon wrote: I see, nested tabs. You need to ensure you've tabs that can be nested. Only tabs manually created within CB > Tab Management and the Contact Info tab will nest. Tabs created via plugins will not nest. It's probably throwing the error, because there are no tabs to nest.

We have several nested tabs displayed nicely

Very strange, wonder if it has to do with the name of your first tab. Please rename your first tab to "TEST" instead of "1+1=3" and see if issue persists. That shouldn't be happening because the object is the tab object and not a blank object. If issue persists after trying the renaming please try disabling tabs within CB > Tab Management that could nest 1 by 1 until it goes away.

No renaming did not change anything.
I looked at the server log but there is no better hint than the warning shown

Please try disabling tabs within CB > Tab Management 1 by 1 until it goes away. This should tell us what tab is causing problems.

The problem comes from CB contact core tab.
If I deactivate all tabs, I have the same warnings.
Putting CB core tab under the main tabs duplicates the warning.

I tried to deactivate CB conditional and CBsubs on CB core tab but it did not work.

Ensure you're not disabling the core content tab. Core fields like user parameters for GID usage are present on it and if it's missing then it'll break some things. If you need to condition it I suggest moving fields to a separate tab and conditioning the new tab to avoid core fields from breaking. Aside from that I've no idea what's doing this as would need backend login credentials to review configuration.