Sorry, I didn't really process your full message. At the end you state your guess these are users with connection problems who got reconnected... based on the relatively small number of times I see this warning, as compared to over-all traffic to the forum, it sounds like I can probably ignore the warning. Thanks for your help.
I tried running nodebb on apache but given I was running under a centos/whm server, it became a nightmare. Now i have nodebb running on Digitalocean but I still get this error like
Is that normal?