With 4.9.1, I noticed AI trying to use Nav Link Proxy to wrong direction (right to left, even I have it set left to right). Had the debug mode on to see the waypoint AI tryes to use and it had route set from land to roof even the only connection is that proxy. Havent seen the issue before in 4.8.
Assuming you have changed the Link Direction in the Smart Link section of the details panel you can expand the Point Links section under Simple Links and change the direction there.
See attachment
Yes, having that setting correctly. 
Seems like the setting is upside down in 4.9. Right to Left is actually Left to Right.
Hi ,
Does this occur in a clean, blank project with no additional content or is it limited to one project? What steps can I take to reproduce this on my end?
Havent tried yet outside of my project but if you set one direction nav link to make AI jump down from tall object, it shouldnt work (unless set “upside down”). I have two nav links in my project. Both worked before and now they didnt. Of course easy to switch the setting, but just reporting.
Just as a test, does it seem to work if you have “both ways” checked? Additionally, do you have the proxy point “left” on the left and “right” on the right or are they reversed?
Sorry for the delay. But yes - cant get the nav links work at all. AI moves to nav link point, but never manages to use it. Dosent matter what setting I have set. Also getting strange behaviour from AI, they sometimes keep changing their move path plan with some 0,5s rate. Not sure what is going on. I will try to search why it could happen. Didnt have these two issues in 4.8.
Do you have a sample project that this is occurring in I can take a look at? I have attempted this on my end but have not received any problems utilizing the nav link proxy in my level.
My project is around 50gb, but I will try to see if there move path changes is caused By me. Maybe its causing also the issue with nav links. Will report back any findings.
Hi ,
Do you have any updated information on the status of this?
Its still a mystery and not working stable. Got AI to move better after disabling them as dynamic obstacles* but these nav links cause still much issues for them. In 4.8 it worked perfectly, but not in 4.9. Cant find what could I have changed wrong.
*https://answers.unrealengine.com/questions/308747/ai-path-getting-updated-constantly.html
Hi ,
I was able to reproduce this on my end and have entered a bug report, UE-21560, to be assessed by the development staff.