Hi!We are using version 3.15.6 + 190108, and we have a problem.Sometimes it appears on the participants screen that a participant has completed the questionnaire, but the answer has not been saved.In the image this happens with the respondent in the last line.On those occasions, we resend the questionnaire, and sometimes, on the second try, it does save the answers, but not always.We have conducted many surveys and surveyed thousands of people in the last 4-5 years, and it happens occasionally, but with increasing frequency.You know that it may be due?

This is really difficult to say. Could be a lot of things, including a bug in Limesurvey. Given that you are running a 2,5 year old version of Limesurvey, if it is a bug it might be long corrected.

There have been quite a few updates to Version LS 3.x since then.

Let's see what others say and if they are aware of such a bug. In anyway, you should really consider updating.

I was about to ask if you have the option "exit and clear survey" activated in your survey, but I guess this should only work until the survey is submitted anyway.

Thank you very much for your answer, holch. 
It is not easy for us to update the version, but we will take it into account.
Thank you again.
 

I know, there is never a good time.

But if you would use a SaaS service they would just tell you on this day and time your installation will be down because we are running an update and there is very little you could do.

So you just need to fix a date, inform everyone and do it. Of course, install the new version in a test environment and test it thoroughly, to avoid suprises. Generally updates within major releases, e.g. from LS 3 to a new LS 3 things should run smooth. At least I had never any problems. And if you have comfort update, it is done in a couple of clicks. Should not take more than 5 to 10 minutes and you are running completely normal again.