Troubleshooting — Display Board Shows PHP Error

Symptoms

• Display board crashes with a visible PHP error
• Error message references queue-board.blade.php and a type property
• Error: "Attempt to read property on string" or similar

Cause

Redis returned a corrupted serialized value for the announcements cache key. The cached value is a PHP string instead of a collection of Announcement model objects. The Blade template then tries to access a property on a string, causing the crash.

Self-Healing Behavior

The QueueBoard render method includes a cache corruption guard:

1. Checks that the cached value is a Collection
2. Filters items to ensure each is an Announcement model instance
3. If any items fail the check, the cache key is deleted and re-queried immediately

This means the error typically resolves on the next render cycle (within seconds).

Manual Resolution

If the error persists after one render cycle:

1. Reload the display browser tab.
2. If still crashing: run php artisan cache:clear on the server.
3. If the issue recurs: check Redis memory usage — a full Redis may be evicting keys in unexpected ways.

What Engineering May Inspect

• app/Livewire/Display/QueueBoard.php lines 136–165 — cache corruption guard
• Redis key: tenant:{tenantId}:display:{screenId}:announcements
• Redis memory usage and eviction policy