LSE clock is off by 5% on Nucleo-L4R5ZI

[SFahr]

Hi, I made a minimum CubeIDE project for a Nucleo-L4R5ZI. It clocks the RTC from LSE using the X2 quartz (NX3215SA-32.768kHz-EXS00A-MU00525) and outputs a 512Hz calibration signal on PC13. The output frequency is only ~492Hz which is a deviation of ~5%. I couldn't find any reasonable explanation. Any ideas?

[SFahr]

By the way:

I just realized that you can output the LSE clock directly to MCO (PA8 on STM32L4R5ZI), so you can scope the decoupled LSE signal directly.

[SFahr]

Hi,

I just tested 3 other Nucleo-L4R5ZI boards: They were all fine with the factory capacitors. It looks like only that one specimen I had on the table was faulty.