another workaround for the browser bug

html/planeObject.js

@@ -2730,6 +2730,10 @@ PlaneObject.prototype.checkVisible = function() {
 
     // recompute seen and seen_pos
     let __now = now;
+    if (isNaN(__now)) {
+        console.error("checkVisible: now is NaN, this is probably a browser bug: https://issues.chromium.org/issues/401652934");
+        __now = g.now;
+    }
     if (this.dataSource == "uat") {
         __now = uat_now;
     }

html/script.js

@@ -324,6 +324,7 @@ function processReceiverUpdate(data, init) {
             now = data.now;
         }
     }
+    g.now = now;
 
     if (globeIndex) {
         if ((showGrid || loStore['globeGrid'] == 'true')
@@ -7851,6 +7852,7 @@ function replayStep(arg) {
 
     last = now;
     now = replay.pointsU[i + 2] / 1000 + replay.pointsU[i + 1] * 4294967.296;
+    g.now = now;
 
     traceOpts.endStamp = now + replay.ival;