Starting a few weeks ago we began getting reports of maps mysteriously vanishing. One minute the map would be there and the next minute the map would be blank, requiring a refresh to get the map to show up again.
We dug into Kumu's code to try and find the culprit but we came up empty handed. Nothing on our end could explain why these maps were disappearing. Even more curious, the bug only seemed to affect Chrome users on Macs (and even then only a fraction of them).
Well, yesterday we finally got to the bottom of it and it turns out this is a bug introduced in Chrome 49. The good news is that the Chrome team knows about the bug and has fixed it in their beta version. The bad news is there's nothing we can do about it until the fix is released in Chrome 50.
In the meantime, if your map suddenly goes blank just resize the window and everything will be fixed. It's an annoying workaround but hopefully the fix will be released in the next few weeks and we can put this one behind us.
Sorry for any frustrations this bug has caused and thank you for your patience while we got to the bottom of it!