Hi @AlejandroMari1
After discussing the problem with developers on the team, here is some information for your reference -
We've tried the Tabs component inside ExB v1.5 and it works fine, the code and result are as follows:
The issue you've encountered seems to relate to how this component was being used. Telling from the error, it happened when the component read theme variables - not getting the correct ones.
To ensure ExB components work fine, there must be a ThemeProvider at the top level of your codes (please refer to more information about React context here) to provide the needed theme variables. If you are in the correct environment, or your app is generated from ExB, this ThemeProvider should have been defined already.
Another possibility is that your custom widget had another ThemeProvider, which was giving the wrong theme variables.
Hope the above information can help in some way. Feel free to provide more information if you'd like as well.