You likely do not have an HDMI over Ethernet extender. Ethernet is a networking protocol. What you likely have is a HDMI over CAT-x extender. You are using either cat-5e or cat-6 or similar, we will just call it HDMI over CAT extender.
It would actually be helpful for you to tell us what extender you are using, because some of them really suck, and some are decent.
I have used dozens of HDMI over CAT extenders, and I have found that they regularly have issues if you get cheap ones. They just aren't built very well. You want a unit rated for 1080p, and you want a unit which has good power supplies. You want to ensure you are using quality HDMI cables, you want to ensure the CAT cable is properly terminated and isn't kinked at all.
So, I have used this with cable boxes that put out 1080i, and I have had no issue at all:
https://www.amazon.com/gp/product/B00G5RBX2Q/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
That's what I call a REALLY cheap solution.
Typically I use HDBT (HD-Base-T) products which have cheap sets starting around $200. I actually can pick very high end gear up off of eBay, but it requires some specialized configuration, so it isn't something I would recommend for most people to get.
There is still no perfect solution to all of this, and the best bet really is to use a HDMI cable if at all possible, but it really isn't always possible, so if using an extender, you just can't get by with the cheapest ones. You've gotta drop 60 bucks at least, and if that doesn't work, you may have to drop a couple hundred bucks.
But, if you can actually run a HDMI cable point-to-point, then that is a far better solution.
