AP9640 (in SMT1500) data log issues

[jmc11]

Have a relatively new NMC card manufactured Aug 2022
SU and AOS are v1.5.1.1, BOOT is v1.3.6.1

No matter how the settings are put, the data log is very inconsistent
Sometimes it logs only a few days, despite a log size of 12 days (1min, 17280)
Sometimes it logs about 1 hour, even though the log size is 1 day (1min, 1440)

Have set the interval to 1min 5min 30min etc, and tried various log sizes up to 20000
But still getting inconsistent and incomplete data logs
Event log seems fine

Hope someone can help. Thank you.