Why does my Corbett Booking website randomly show a server error?

I am working on a travel booking website similar to Corbett Booking. The website is working fine most of the time, but sometimes it suddenly shows a “We had a server error” message without any clear pattern.

This issue is not constant, which makes it difficult to identify the root cause.

What I have already checked:

Hosting server status (no downtime found)

Basic caching setup

Database connection (appears stable)

My concern:

I want to understand what could be causing this kind of intermittent server error in a web application.

Specifically:

What are the common reasons behind random server errors in a booking website?

How can I properly debug backend or server-side logs to find the issue?

What are the best practices to prevent such issues in PHP/WordPress-based travel websites?

Any guidance or debugging approach would be really helpful.