RA4M2 MCU RTC forward deviation

Hello everyone,

We saw rtc 15 sec forward deviation in 5 minutes, we using loco clock source.I added below my rtc configuration:

I could use to sub-clock. can you help what's configuration the rtc for 2 option(loco and sub-clok).

some time I see deviation but some time i dont see deviation. The Temperature was stilled in the room. The desk hasnt vibration.

Thank for reply