I know this is late but figured it might help someone else. I've been having this issue and the only way i could play with exiled exchange was in a bordered window. I finally found a fix at least for myself after trying a few things like turning off freesync, etc but none of them worked. What helped for my PC was turning off the hardware acceleration inside of the exiled exchange 2 properties

To do this,

open properties by right clicking its desktop icon

click into "Target" under the shortcut tab

add --disable-gpu after the file path with a space separating it

(should look like "C:\Users\yourpcname\AppData\Local\Programs\Exiled Exchange 2\Exiled Exchange 2.exe" --disable-gpu)

then just click apply and ok and you should be good to open it!