These are the marketing bullet points for that switch.
Items 2, 3, and 5 are all red flags in my book when 5 and 6 are combined that sets off further alarms that this switch should be avoided at all costs as the network would be more reliable if it were wired with cans and string (or smoke signals).
Seriously, this POS is the answer to a question that no one ever asked. If the customer has a door that needs to be propped open or needs a parking block in his garage then #4 on that bullet list suggests that it might be useful. Otherwise it shouldn’t ever be plugged into an actual network.
Joking aside, I’m 98% certain that switch is the problem. Track down a Netgear GS-108 (the blue one) or a Cisco SG110-08 and there should be an improvement.
As a total aside (and for the record) this is fine. Technically regular CAT5 doesn’t have the proper configuration to certify for gigabit (hence the creation of 5e), but it’s really close and in most residential applications it works just fine. About 50% of the wire in my old house was CAT5 (with the other 50% CAT5e) and the two were indistinguishable in practice. I’ve yet to see a residential application in which CAT6 makes sense and when I wired my new house last month I did 39 drops of CAT5e.