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IDProjectCategoryView StatusDate SubmittedLast Update
20158Bug reportsSurvey participants (Tokens)public2025-07-03 01:312025-07-03 09:22
Reporterdavid_b Assigned To 
PrioritynoneSeverityblock 
Status newResolutionopen 
Product Version6.6.x 
Summary20158: 503 error related to debug status
Description

When debug = 0 in config.php, adding participants or sending email invitations fails (blue spinner with HTTP 503 error). Setting debug = 1 or debug = 2 resolves the issue. The problem persists across fresh installs (v6.10 and v6.15), browsers, and environments on my shared hosting at VentraIP.

Environment
LimeSurvey Versions Tested: 6.15, 6.10 (fresh installs)
PHP Version: 8.2
Hosting: VentraIP shared hosting

I have completed full, fresh installs using both Softaculous and Installatron and the issue is reproducible on this provider.

Same survey works on other people's services. (holch on LimeSurvey community forum).

VentraIP is looking into it. They tell me that 503 represents "cPanel indicates that your I/O limits have been reached, which will cause a 503 error; however, doing a live test of your I/O I cannot see anything major being transferred."

Is there something different between the debugging settings that might explain the problem?

Steps To Reproduce

Steps to reproduce

Set debug = 0 in config.php (e.g., /home/belavyco/survey.belavy.com/application/config/config.php).
Navigate to Participants → Add new participant or Send email invites.

Expected result

New participant screen

Actual result

Observe: Blue spinner persists indefinitely.
Console error: Failed to load resource: the server responded with a status of 503 ().

TagsNo tags attached.
Bug heat2
Complete LimeSurvey version number (& build)6.15.0, 6.10
I will donate to the project if issue is resolvedNo
BrowserSafari, Chrome (including incognito/private modes)
Database type & versionMySQL/MariaDB - I think 10.6
Server OS (if known)
Webserver software & version (if known)
PHP Version8.2

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david_b

david_b

2025-07-03 09:22

reporter   ~83016

Hosting provider found the issue. Here's a summary:

Root Cause Summary
The 503 errors during participant management operations (debug=0) were caused by incompatibility between LimeSurvey and Monarx (VentraIP's anti-virus/malware scanner). Specifically:

Silent Process Termination: When debug=0, PHP script failures triggered by Monarx caused LiteSpeed to return 503 errors ("Service Unavailable").
Debug Mode Masking: With debug=1/2, errors were displayed visibly instead of terminating silently, avoiding 503s.
No Resource Issue: Server-level checks confirmed no memory/CPU/disk constraints (confirmed via LVE limit tests).
Resolution Path
Immediate Fix: Disabling the Monarxprotect PHP module restored functionality.
Permanent Solution: VentraIP infrastructure team is rolling back the problematic Monarx update.
Workaround: Users can manually disable Monarx via "Select PHP Version" in hosting control panel if needed.
Key Technical Insight
"Monarx interfered with PHP process handling, causing silent termination (triggering LiteSpeed 503) when debug mode hid errors. Resource increases (memory/IO limits) couldn't resolve this application-layer conflict."

Issue History

Date Modified Username Field Change
2025-07-03 01:31 david_b New Issue
2025-07-03 09:22 david_b Note Added: 83016
2025-07-03 09:22 david_b Bug heat 0 => 2