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LimeSurvey version: [see right hand bottom of your LimeSurvey admin screen]
Own server or LimeSurvey Cloud:
Survey theme/template:
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LimeSurvey Community Edition Version 6.15.5+250724 
Private Server running Ubuntu 11.4.0
Survey theme:  Bootstrap Vanilla, customized

We run a survey every month for our organization, about 250-300 respondents.  Every month I get a small number ( 4-8 ) people complain because they get an error message AFTER they click Submit.  It is a one page survey.  The error message is *usually* a 400: Bad Request message, but not always.  I have customized the "layout_errors.twig" to inform the user that the survey is open only between 1st and 10th of the month.  But, they are getting the message even when the survey is OPEN during the correct window.  Again, some are getting a 400: Bad Request error, sometimes no error number is reported.

It's impossible for me to duplicate it.  The errors are coming from Mac/Safari and Windows/Chrome.  

Only about 1% of the respondents report an error.  If they retry the survey page, it almost always works the 2nd time, but the user has to re-enter their data, which they are not happy about.  I have my php session timer set to 2 hours, and the respondents will get the error even after just 5-8 minutes entering their answers.

I have tried to figure out what error(s) the server side (apache or LimeSurvey) is seeing, but I can't figure out what to look for or where to look.

any suggestions?
thanks,
Rick

Error 400 indicates some kind of server issue. I don't think it has to do with the session or anything like that (you can never exclude it, but I think chances are little).

I think you will have to try to get any logs from the server to see what happened.

Do you send admin notification emails in your survey?

In general, we do not recommend one page surveys, for this very reason. If something goes wrong, everything is lost. Of course, this is not a big deal with very short surveys, but if there are more than 2-3 questions, I always recommend to separate them, either by using question per question or group by group. These are usually the standard anyway.

Is this a closed (using tokens) or an open survey?

Thank you for taking the time. Ive looked all over for the server logs, including the Apache 2 logs and can't find any information that helps. We used to have the survey on several pages and had too many complaints.

Open survey

holch wrote:

Do you send admin notification emails in your survey?

What about the sending of admin notifications?
When there are problems with sending the email (Email server doesn't respond, etc.), Limesurvey likes to throw errors.

Sorry, I missed that question.

Yes, we send out admin notifications. The basic admin email goes to me directly with just the name of the person who completed the survey (entered by the user in the survey). The admin email goes to the individual with their responses; the user enters their own email address with validation of the domain name = @ourdomain.org. When there is no error, the emails are sent out correctly. I have scoured the mail logs in /var/log (mail.err, maillog, maillog.processed, syslog) and I don't see any error messages related to this failure. I am stumped.

Thanks again for your assistance, on your own free time. I do appreciate it.