Strange Time Issues

I am getting this in the log:

7/13/22 00:34:22 timeSync: adjusting RTC by 75540
7/13/22 01:34:22 timeSync: adjusting RTC by 75540
7/13/22 02:34:22 timeSync: adjusting RTC by 75540
7/13/22 03:34:22 timeSync: adjusting RTC by 75540
7/13/22 04:34:22 timeSync: adjusting RTC by 3540
7/13/22 05:34:22 timeSync: adjusting RTC by 3540
7/13/22 06:34:22 timeSync: adjusting RTC by 3540
7/13/22 07:34:22 timeSync: adjusting RTC by 3540
7/13/22 08:34:22 timeSync: adjusting RTC by 3540
7/13/22 09:34:22 timeSync: adjusting RTC by 3540
7/13/22 10:34:22 timeSync: adjusting RTC by 3540
7/13/22 11:34:22 timeSync: adjusting RTC by 3540
7/13/22 12:34:22 timeSync: adjusting RTC by 32340
7/13/22 13:34:22 timeSync: adjusting RTC by 32340
7/13/22 14:34:22 timeSync: adjusting RTC by 39540
7/13/22 15:34:22 timeSync: adjusting RTC by 39540
7/13/22 16:34:22 timeSync: adjusting RTC by 39540
7/13/22 17:34:22 timeSync: adjusting RTC by 39540
7/13/22 18:34:22 timeSync: adjusting RTC by 39540

This is strange as the numbers are consistent (3540 seconds is 59 minutes; 32340 is 8 hours and 59 minutes; 39540 is 8 hours and 59 minutes; 75540 is 20 hours and 59 minutes). This is a new DS3231 RTC. The RTC obviously is identified by the firmware:

7/12/22 00:30:31z ESP8266 ID: 750129, RTC M41T81 (68)

Any ideas? could it be a malfunctioning RTC (more reasonable - what have I done wrong?)

DS3231 is not supported. The IoTaWatt can identify the RTC used to the extent that it is either a PCF8523 or M41T81.