diff --git a/documentation/sphinx/source/release-notes/release-notes-620.rst b/documentation/sphinx/source/release-notes/release-notes-620.rst
index 474af82201..5867dff174 100644
--- a/documentation/sphinx/source/release-notes/release-notes-620.rst
+++ b/documentation/sphinx/source/release-notes/release-notes-620.rst
@@ -4,6 +4,7 @@ Release Notes
 
 6.2.33
 ======
+* Fixed an issue where storage servers could shutdown with ``unknown_error``. `(PR #4380) <https://github.com/apple/foundationdb/pull/4437>`_
 * Fix backup agent stall when writing to local filesystem with slow metadata operations. `(PR #4428) <https://github.com/apple/foundationdb/pull/4428>`_
 * Backup agent no longer uses 4k block caching layer on local output files so that write operations are larger. `(PR #4428) <https://github.com/apple/foundationdb/pull/4428>`_
 
diff --git a/fdbserver/storageserver.actor.cpp b/fdbserver/storageserver.actor.cpp
index 2fa187ceb2..1bda413d16 100644
--- a/fdbserver/storageserver.actor.cpp
+++ b/fdbserver/storageserver.actor.cpp
@@ -367,12 +367,19 @@ public:
 			UID UIDofLongest;
 			for (const auto& kv : startTimeMap) {
 				const double currentRunningTime = currentTime - kv.second;
-				if (longest < currentRunningTime) {
+				if (longest <= currentRunningTime) {
 					longest = currentRunningTime;
 					UIDofLongest = kv.first;
 				}
 			}
-			return { longest, keyRangeMap.at(UIDofLongest) };
+			if (BUGGIFY) {
+				UIDofLongest = deterministicRandom()->randomUniqueID();
+			}
+			auto it = keyRangeMap.find(UIDofLongest);
+			if (it != keyRangeMap.end()) {
+				return { longest, it->second };
+			}
+			return { -1, emptyKeyRange };
 		}
 
 		int numRunning() const { return startTimeMap.size(); }