I think the Hikvision cube can be powered over POE and yet use its WIFI--pretty sure I asked recently and fenderman said yes, plus my fiddling in firmware indicates it can probably be done.
I am using a hikvision cube over wifi successfully but NOT for storage. Storage for it is over SD. As nayr says, you can just forget wifi if you want 24/7 constant frame rate without drops. I am able to pull data from the camera reliably enough but I won't trust wifi to deliver even a 5 mbps stream consistently and reliably. At least in my area (suburbs--would be worse in urban) there is too much crap in the air causing issues. Too much errant interference. In fact, my respect for wifi goes down over time. I now wire everything I can; the only stuff that isn't wired are my apple devices and a laptop that moves around the house (and that cam I mentioned). PS4, desktop are all wired. Just sick of dealing with wifi nonsense.
Test some connections before trying dielectric. I think probably the advise for coax is better.
I did have an RJ45 port exhibit green discoloration when I looked at it a month back. It had been disconnected and hanging free for 6 months outside but NOT exposed to direct moisture. I only saw corrosion on one of its pins, which was strange; made me wonder if a drop of water had somehow gotten on only that pin. However, until I scraped it down I couldn't get that connection to work. I've since wrapped it in cling wrap and tightly elastic banded it until I need it again. I imagine even moderate corrosion if you ever get it is no huge problem for already-installed cameras, since the connection is already made.
