Our DHCP sometimes does not receive requestpacket from client

So, we have had this problem for a while now.

Sometimes the DHCP does not receive the requestpacket from a client when the client is trying to get an IP-address.

The reason why we haven't found a solution is because this only happens sometimes. Most of the time the clients get their IP-addresses just fine.

The problem can persist for a single client for 15 minutes to 1 week, it is completely random. This has to be a networking issue.

Have any of you had any similar problems before?