How to determine what is the problem on opencart?

Question

opencart

There is an online store with 200 products (approximately)
The problem is this: sometimes (arbitrarily) some users do not load pictures. That is, they open, let's say, a product catalog page, and there are no images on the products. When the page is refreshed, this problem almost always disappears, the same trouble occurs on the other pages of the site.
I suspect that this is a weak hosting, since there are no errors, and no problems are observed at night and in the morning.
What can you say about this? Perhaps the cache needs to be enabled?

Answer 1

The static is distributed by nginx, I hope, and not by Apache?