Dexcom Receiver Failure - Root Cause Determined but Dexcom has Not Yet Found the Problem Code.

tl;dr: For 15 minutes after beginning or ending a sensor session, do not power the device down.

Today, for the 4th time in a year (possibly 18 months), I had a receiver fail to turn on. When turning it on it would go into the standard boot screen, with the green progress bar. It gets to the final little green box and then buzzes and restarts. Rinse/Repeat forever.

Because this has been a repeating issue for me I've been keeping close track of the actions I take with the receiver, hoping that I'd figure out the pattern. And this time I did.

This morning I ended a sensor session on the receiver and then turned the receiver off. This evening, first time turning it on since this morning, the issue occurred. The previous time this happened to me (March-ish), I'd gone through the same steps. Perfect! A pattern!

Speaking with Dexcom Tech Support now and they confirmed that they very recently also figured out the pattern and have told tech support personnel to advise patients the following:

1. For 15 minutes after beginning a sensor session, do not power the device down.

2. For 15 minutes after ending a sensor session, do not power the device down.

However, they have not yet found the faulty code in the receiver.

My guess (based on my experience writing bluetooth low energy code), if the device loses power in the period when a bluetooth pairing is beginning or ending (5-8ish minute period) it can get into weird states. Depending on how the receiver is coded, that weird state may be ending up as an error code. Now, I'd expect a restart and/or system restart (paperclip in back of receiver) to reset that error, but it appears it is not. This is where embedded systems coding gets really hard.....there is some error code being stored in persistent memory that is not getting reset. I asked the very helpful tech support woman to pass that little tidbit along to the engineers - I hope it helps them find the root line of code.

Dexcom is not, currently, pro-actively notifying patients about this issue. They are only educating if a patient calls in with the fault. I expressed my concern with that approach as now I'm going to be without a CGM for 36 unplanned hours. I also suggested that when they send out new receivers they include a little note informing patients of the issue. At least then when we get a new receiver for any reason (like everyone does every 12 months anyway, generally) we'll be informed of the problem.

She is passing my concerns and thoughts up the right channels.