I recently encountered a strange but constant issue with a new network I was swapping in (replacing 8 MR3201As that kept locking up with 8 OM1Ps). I was testing them in my home with them all plugged in in the same room (so no signal issues at all). The problem seemed to constantly recur on the r2694 firmware so I upgraded them all to r3842 and the issue seemed to lessen. After some further investigations we found that the checkins were actually timing out
. The reason? In New Zealand we have data caps (I have 60GB/Phone for $100NZD/month) and once you exceed that you are either paying around $2/GB overage or slowed to dial-up speed (64Kbps). Our ISP slows to Dialup speed or you can double the cap for $30 (not worth it considering the internet renews in two days). Anyway, I shared the USB iPhone tethering over Ethernet to the Gateway node using my MacBook Air and lo and behold: the issue disappeared and I could no longer reproduce it. Plugging them back in to the dialup I could no longer successfully make them checkin every time.
Solution: Make sure you have broadband