Drobo 2nd Gen all lights flashing orange/green

All 4 drive lights on My 2nd Gen Drobo have started flashing alternately green then orange. Been going on for about an hour now. Data still available but Dashboard no longer recognises device. Have tried raising support case which I realise I’ll have to pay for but in meantime any info/advice appreciated.

Update on above. Data became no longer available so rebooted Drobo. On boot completion single red light appears temporarily against 1 drive then the original light sequence starts ie all orange to green repeated. A pop up then announced data rebuild in progress and I now have dashboard back. Original time estimate was 1 hour but now it’s saying 16 hours. I have 11 TB capacity with around 2.5 TB of stored data. So I’ll leave it to do its thing but if the drive with the temporary red light is about to fail why doesn’t it simply show that permanently red and the rest green. That way I know to replace that drive.