Slow/no connection after adding a switch

[mrv03]

So my buddy has the TP‑LINK Archer CR700 modem/router.  And he is using a netgear (its a gigabit model) power-line adapter to get ethernet to his room over his outlet plugs.  So to do what he wanted he needed more than one ethernet port, so i sent em a link to this TP-link gigabit switch and he bought it since it said plug and play it should work.  And everything i searched said that particular setup should work fine.  So when he puts the switch in, it originally worked ok for about 10 mins then his ping shot up to like 30k and the computer would lose connection.  Everything works fine if he has his pc directly plugged into the ethernet port of his outlet adapter.  Just adding this, dunno if its relevant, but he gets only 4 megs down and 10 up when i have em do a speed test, but over wireless he gets like 55 down and 10 up.  Why would the powerline adapter give him the full upload speed but not the full download?  Also whenever i tried to use teamviewer to help him out, his router wasnt having any of that, like 3 or 4 mins into using it his router just shut down and didn't allow any internet connection over wifi or wired till he reset the router, and the second time we tried it was like 60 seconds on teamviewer before it did the same thing.