Hello,

Thank you for reaching out, and I am happy to help!
This depends on how big the website is, so if the website has a huge theme or a lot of plugins, it’s quite possible that the memory limit was reached.
Also, which module are you using Redis as a caching method for in W3 Total Cache?
It’s also possible that the Redis memory is bloated, so you should also check this
Check Redis memory usage

redis-cli info memory
redis-cli info stats

See if your Redis instance is bloated.

Sometimes, memory is genuinely too low for your site’s workload. If after cleaning up the cache usage, you still hit the limit, raising to 768M or 1G is fine:

memory_limit = 1G

in php.ini or

I hope this helps!

Thanks!