Wierd stretching 9:16 resolution

Hi,
I am implementing multiplayer application where listen server acts as first person character and clients are “spectating” that character with view or with some offset. Everything seems to be working when using standard 16:9 resolution like 1920x1080. However my target platform has multiple monitors(clients) in portrait orientation so 9:16 resolution is used 1080x1920.
I am experiencing wierd vertical stetching or kind of “fish eye” effect as you can see on attached (link:video). I tried to supply own APlayerCameraManager with DefaultAspectRatio = 0.5625f; or bDefaultConstrainAspectRatio = true; set in constructor (that was just trial-error, i dont really know whats the problem).
Second problem is with connecting client whose viewport has black stripes and standard ratio 16:9 as you can see on link:screenshot.
I am testing this editor as New Editor Window with this settings link:screenshot. However problem also persists when project is packed and running in fullscreen mode.
Can someone point me to right direction what is causing this behavior?
Thanks in advance

I was able to solve second problem by setting GetCameraComponent()->AspectRatio = 0.5625f; in actor/pawn’s contructor which is used as ViewTarget by client player controller. However wierd stretching persists.

Please promote your comment to an answer and mark it as correct to close it.

My problem was only partially solved and main problem still persists so I wont mark it as correct.

I was able to solve my problem by setting aspect ratio axis constraint in PlayerController class.
ULocalPlayer* player = GetLocalPlayer();
if(player)
{
player->AspectRatioAxisConstraint = EAspectRatioAxisConstraint::AspectRatio_MaintainYFOV;
}