(Service Check Timed Out) in RAW edition 1.6.0p11 (centOS 8)

If it also happens on small devices then it looks more like a general problem.
You can only inspect the response of your devices on the command line with a call like “cmk --debug -vv hostname”.
If you see that all devices are slow at the interface table then you have a general problem with all the devices. If you have other brands available to compare you will see very different behavior.