Please help us help you and fill where relevant:
LimeSurvey version: 6.15.0+250623 
Own server or LimeSurvey Cloud: Self Hosted
Survey theme/template: Custom
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We updated to the latest version via the Comfort update and now I am unable to create a new question in any survey ... existing or new?

When I click the add question button an error is thrown in the console which takes me to this page 
https://myserver/index.php/questionAdministration/create?surveyid=741298&1750931075075

And on this page this is displayed
500: Internal Server Error - Failed to generate title for question

Is there anything I can do to resolve this or do I need to "downgrade" to the older version?

 

Since you are a paying customer (for ComfortUpdate), you can contact LimeSurvey support directly.

Before anything, did you clear the browser cache as well as the asset cache within Limesurvey?

If that doesn't help: As Tpartner says, you seem to be a paying customer of Comfort Update, so you can get in touch directly with the Limesurvey GmbH support (don't let them tell you for the Community Edition there is no support - which is true - but in your case this is support for Comfort Update).

It appears that the issue is related to the prefixes in the survey .. apparently you have to use Q for the question code prefix, SQ for the subquestion prefix and A for the Answer code prefix and then set inherit on in the survey .. there is a fix coming

 

Thanks for the update and keeping us in the loop.