Why is the switch unavailable at regular intervals?

Question

Network administration

An interesting problem, but I could not solve it yet.
There is an office with several vlan.
Device management is moved to a separate vlan.
There are 5 switches. 4 - DGS-1210-28 and one - 1100-24.
That's just the problem with 1100. It is available for about 5 minutes, then disappears for 15.

But if you ping it from the gateway at any time, it immediately appears for 5 minutes.
The problem is only with access to the web. As a switch, it does everything without problems.
Has anyone encountered something similar?
Maybe I forgot to clarify some important information.

Answer 1

5 minutes? A very typical MAC Learning cache timeout value. Working hypothesis - responds to the wrong port or the wrong vlan. Perhaps a vlan configuration error. Or firmware error