diff --git a/brozzler/browser.py b/brozzler/browser.py
index c0cb3ee..4a8f608 100644
--- a/brozzler/browser.py
+++ b/brozzler/browser.py
@@ -356,13 +356,12 @@ class Browser:
             # tell browser to send us messages we're interested in
             self.send_to_chrome(method='Network.enable')
             self.send_to_chrome(method='Page.enable')
-            self.send_to_chrome(method='Console.enable')
-            self.send_to_chrome(method='Runtime.enable')
-            # Network.requestIntercepted needs more work...
-            #self.send_to_chrome(
-            #    method='Network.setRequestInterception',
-            #    params={'patterns': [{'urlPattern': '*'}]})
-
+            # Enable Console & Runtime output only when debugging.
+            # After all, we just print these events with debug(), we don't use
+            # them in Brozzler logic.
+            if self.logger.isEnabledFor(logging.DEBUG):
+                self.send_to_chrome(method='Console.enable')
+                self.send_to_chrome(method='Runtime.enable')
             self.send_to_chrome(method='ServiceWorker.enable')
             self.send_to_chrome(method='ServiceWorker.setForceUpdateOnPageLoad')
 
@@ -661,6 +660,7 @@ class Browser:
                 method='Runtime.evaluate', suppress_logging=True,
                 params={'expression': behavior_script})
 
+        check_interval = min(timeout, 7)
         start = time.time()
         while True:
             elapsed = time.time() - start
@@ -669,7 +669,7 @@ class Browser:
                         'behavior reached hard timeout after %.1fs', elapsed)
                 return
 
-            brozzler.sleep(7)
+            brozzler.sleep(check_interval)
 
             self.websock_thread.expect_result(self._command_id.peek())
             msg_id = self.send_to_chrome(
diff --git a/brozzler/chrome.py b/brozzler/chrome.py
index c70296f..cbca3e5 100644
--- a/brozzler/chrome.py
+++ b/brozzler/chrome.py
@@ -250,10 +250,16 @@ class Chrome:
         # XXX select doesn't work on windows
         def readline_nonblock(f):
             buf = b''
-            while not self._shutdown.is_set() and (
+            try:
+                while not self._shutdown.is_set() and (
                     len(buf) == 0 or buf[-1] != 0xa) and select.select(
                             [f],[],[],0.5)[0]:
-                buf += f.read(1)
+                    buf += f.read(1)
+            except (ValueError, OSError):
+                # When the chrome process crashes, stdout & stderr are closed
+                # and trying to read from them raises these exceptions. We just
+                # stop reading and return current `buf`.
+                pass
             return buf
 
         try:
diff --git a/brozzler/js-templates/umbraBehavior.js.j2 b/brozzler/js-templates/umbraBehavior.js.j2
index 172cdfd..7931a62 100644
--- a/brozzler/js-templates/umbraBehavior.js.j2
+++ b/brozzler/js-templates/umbraBehavior.js.j2
@@ -43,6 +43,7 @@ class UmbraBehavior {
 
         var documents = [];
         documents[0] = document;
+
         var iframes = document.querySelectorAll("iframe");
         var iframesLength = iframes.length;
         for (var i = 0; i < iframesLength; i++) {
@@ -54,23 +55,31 @@ class UmbraBehavior {
                 // console.log("exception looking at iframe" + iframes[i] + ": " + e);
             }
         }
+
         var documentsLength = documents.length;
         for (var j = 0; j < documentsLength; j++) {
             if (closeSelector) {
                 var closeTargets = documents[j].querySelectorAll(closeSelector);
                 for (var i = 0; i < closeTargets.length; i++) {
-                    this.doTarget(closeTargets[i], "click");
+                    if (this.isVisible(closeTargets[i])) {
+                        closeTargets[i].click();
+                        didSomething = true;
+                        break;
+                    }
                 }
             }
+
             if (firstMatchOnly) {
                 var doTargets = [ documents[j].querySelector(selector) ];
             } else {
                 var doTargets = documents[j].querySelectorAll(selector);
             }
+
             var doTargetsLength = doTargets.length;
             if (!(doTargetsLength > 0)) {
                 continue;
             }
+
             for ( var i = 0; i < doTargetsLength; i++) {
                 if (!repeatSameElement && this.alreadyDone.indexOf(doTargets[i]) > -1) {
                     continue;
diff --git a/setup.py b/setup.py
index 27eb4b6..ef5d945 100755
--- a/setup.py
+++ b/setup.py
@@ -32,7 +32,7 @@ def find_package_data(package):
 
 setuptools.setup(
         name='brozzler',
-        version='1.5.7',
+        version='1.5.8',
         description='Distributed web crawling with browsers',
         url='https://github.com/internetarchive/brozzler',
         author='Noah Levitt',