diff -u --label /usr/share/emacs/28.0.50/lisp/window.el.gz --label /home/user/src/patches/window.el /tmp/jka-comAXCNZa /home/user/src/patches/window.el
--- /usr/share/emacs/28.0.50/lisp/window.el.gz
+++ /home/user/src/patches/window.el
@@ -5073,14 +5073,9 @@
   (setq window (window-normalize-window window t))
   (let* ((buffer (window-buffer window))
 	 (quit-restore (window-parameter window 'quit-restore))
-	 (prev-buffer
-	  (let* ((prev-buffers (window-prev-buffers window))
-		 (prev-buffer (caar prev-buffers)))
-	    (and (or (not (eq prev-buffer buffer))
-		     (and (cdr prev-buffers)
-			  (not (eq (setq prev-buffer (cadr prev-buffers))
-				   buffer))))
-		 prev-buffer)))
+	 (prev-buffer (car (cl-find-if-not
+                            (lambda (buf) (eq (car buf) buffer))
+                            (window-prev-buffers window))))
 	 quad entry)
     (cond
      ((and (not prev-buffer)

Diff finished.  Tue May 11 22:00:30 2021