My wife just got a 2020 Impreza Sport and came home tonight complaining about it being unstable on wet roads. She said it was all over the lane and the Eyesight function was going on and off. So we went into town, took the freeway and I drove. I turned off the lane assist (keeps you in your lane) and didnt have any issues. I had a few instances with hydroplaning, but it wasnt bad. She commented that there was more water on the road than where we were at the time of our test drive  I told her to turn off the lane assist the next time the roads got bad and see if it still does it.

Anyone else have Eyesight/Lane assist ever encounter this?

I've never driven anything that fancy and probably never will. I can see cameras having a problem with reflected light on wet roads.

Found this on a Subaru site. - the EyeSight camera lens (it’s set of eyes) is located at the top of the windshield.

maybe look thru the manual for more eyesight and lane assist info/warnings?

I know all car manufacturers do not recommend using cruise control in bad weather, probably best to use as little automated drive assist as possible in rain & snow.

I keep lane assist off by default unless on a major multi-lane highway with the cruise on.
On smaller single lane and back roads the lane assist seems to want to make unnecessary micro adjustments.

I would imagine it would have to do with the Eyesight loosing its ability to track the lanes, or as stated earlier the reflected light off the water. I don't have eyesight on my outback, but I have had some experience, and if it cannot see the lines in the road it can get real confused. 

Eyesight shuts off when it cant see the road, it will tell you its off up on the display. The issue is with the lane assist control, so its turned off for now. I think the best time to use all of this is when your in heavy traffic and going at slower speeds. Just turn the CC on and let the car basically drive itself 

On a side note - Just installed front and rear dash cams, that was fun. Had it on the 05 OB and running the cable from front to rear wasnt too bad, no sunroof or airbags to deal with. Quite the hassle on this one, getting past the airbags and sunroof. Had to make sure it didnt interfere with the airbags or the Eyesight cams