Switch has difficulty talking to SITECOM LN-300 Print Server

I've recently bought a TP-LINK TL-SG105 switch.

Connected to the switch is

• a TP-LINK AV600 powerline adaptor
• a Sitecom LN-300 print server connected to a HP2300 Duplex printer (ethernet to parallel port)
• a StarTech PM1115U2 print server connected to a HP Photosmart C4580 (ethernet to usb)

With this network combination for printing I find that -

• The HP 4580 always connects to the network and a test print gets printed in a timely manner.
• The HP 2300 has difficulty connecting to the network and if a test print gets printed it takes it's time.

My previous "network" for printing was to -

• connect the Sitecom LN-300 print server directly to the TP-LINK AV600 powerline adaptor. In this combination the HP 2300 printer always connects to the network and a test print prints in a timely manner.
• connect a 5m USB cable directly from my main PC to the HP 4580 printer. In this combination the HP 4580 printer always connects to the network and a test print prints in a timely manner.

What I don't understand is why the switch -

1. finds it difficult to send packets to a SiteCom LN-300 print server
2. has no problem sending packets to a StarTech PM1115U2 print server

.