...what happens if your reset the repeater? Or, if you connect directly to the router upstairs, does that correct the issue too?

Also, because it sounds like you're using an ethernet cable directly from your computer to the repeater, if this is a Windows 10 computer, have you tried visiting the computer manufacturer, or the ethernet adapter manufacturer's website and downloading, then installing an updated ethernet driver for your computer? If not, please do.

Let us know.

Hope this helps.

Grif