For us to be able to investigate this issue please attach a 2 question sample survey demonstrating the issue, either as .lss file (survey structure) or (even better) as .lsa file (survey archive).

Just attach it to this issue and we will have a look.
Thank you!

Please also try updating to the latest version 3.27.12+210816.

Could be an issue with Mac (safari), I will try to reproduce this.

Unfortunately, I am not able to produce a sample survey where the issue occurs consistently. A sample survey with 4 groups with and 4 questions did produce the issue at first, now it no longer occurs, even with 6 groups and 6 questions. Can I confidentially share an existing survey where the issue occurs consistently? Does the "private" option ensure that? I do not want the survey to be shared publicly.

I cannot reproduce this issue on Safari (version 14.1.2). I also tried on chrome with no luck. You can share a file and mark it as private and only admins and developers can see it.

Updating to Version 3.27.12 did not resolve the issue. I have moved the survey to an older LimeSurvey installation on a different server. This server is running Version 3.25.20. The issue does not occur here. So the problem was introduced somewhere between Version 3.25.20 and Version 3.27.10.

Thank you for the information. I am using version 3.27.10 to test. This might take some time to reproduce since it happens randomly.

We are using table based session files. I'm not sure if this is relevant.

@gsoto, feel free to attach the template used if your guess is that this casues the problem (I have my doubts).

@galads / @ollehar, please mark the ticket "private" if the theme is uploaded.
This issue really becomes a show stopper for this customer and I have no real clue what may cause this. We have not received any similar problem reports from other customers.

I will test with the theme you uploaded. I could not find any issue with the core themes on safari

If it can't be reproduced with the standard survey themes, I can only assume it's faulty HTML or JS in the custom theme.

In the meantime, a user has reported an instance of the issue occurring on our version 3.25.20. We have now set up a separate LimeSurvey instance of an even older version (3.23.1). So far, we have not encountered the issue in this version. But obviously, going back further in time cannot be the solution.

@ollehar, the adjustments we made only included .twig or .css file adjutsments. We have taken all other core files form the vanilla theme.

@gsoto, if I remember correctly, the issue were also showing up a few times using the shipped vanilla theme?

@Mazi You should try the forum for help with debugging the custom theme.

@gsoto We only support bug fixes for the latest LS versions. For LS3, it's 3.27.17.

@Mazi Yes, the issue has occurred a few times using the shipped vanilla theme. With the custom theme, we have encountered the issue a lot more cosnistently. It is impossible for us to determine what factors precisely cause the issue.

@ollehar Yes, I understand that you won't debug old versions. The issue does not (or hardly) occur in the old version. This suggests that a bug was introduced since that version and is present in the latest version.

@ollehar, I am sorry, but I am working with this software for more than 14 years and have dealt with > 1000 Limesurvey projects. I don't think there is someone else with more experience at the forums.
Furthemore, the customer reports that the problem also shows up with the vanilla theme so it is not related to any edits we made to the templates.

@gsoto: I think what we need is a link to a test survey at the latest 3.x version and then some detailled instructions on how we can safely reproduce this. That would be the starting point to track it down.

OK, well, then as usual it's the problem of being able to reproduce. :) Any type of more info is welcome.

I have 3 weeks ago privately shared a link to a survey where the issue occurs for us consistently. @galads, is there any progress on reproducing the issue? With the latest update to 3.27.17, it still occurs.

I have tried several times on safari to reproduce this issue but I cannot.