Update 29/04/2026: This is a confirmed issue with the Forerunner 55 and seems to be linked to a firmware update – The user reported it working the first day, but not after that, so we suspect it did a firmware update in the night. There are a couple of Garmin bug reports open about it: (https://forums.garmin.com/developer/connect-iq/f/discussion/435465/problem-with-accelerometer-on-forerunner-55/2028423, https://forums.garmin.com/developer/connect-iq/i/bug-reports/bad-accelerometer-data-captured-by-fr55-after-latest-update). So if you have a Forerunner 55, Disable Automatic Updates.
Is anyone using a Garmin Forerunner 55 with OpenSeizureDetector? A user has reported a strange behaviour where the first time they used it, it worked correctly, but since then it has only been sending data every 20 seconds rather than every 5 seconds. (https://github.com/OpenSeizureDetector/Garmin_SD/issues/82)
If you are using a Forerunner 55, please will you send me a log file off the watch? (you need to put an empty text file in GARMIN/APPS/LOGS called GarminSD.txt, then run the app for a couple of minutes, then when you re-connect the watch to the computer, GarminSD.txt, and possibly GarminSD.bak will contain data that we can analyse).
Thanks
Graham (graham@openseizuredetector.org.uk)