Beautiful example of the buggy doors.

Sneaking up on the Githyanki, Wyll can't cast a surprise eldritch blast because the door opening blocks the way.

[Linked Image from i.imgur.com]

But they can still sneak 50 cm further on,to pass across the door opening , and then the spell can hit target.

[Linked Image from i.imgur.com]

Please avoid this in your future games, Larian.