How to improve accuracy of CMWX1ZZABZ-091 RTC

[MAebl]

I'm using the B-L072Z-LRWAN1 with the CMWX1ZZABZ-091 LoRa® /Sigfox™ module (Murata)

The internal RTC is inaccurate and I'm seeing 10 seconds loss per day for some modules. 

My question is, why could this be? Datasheet says 1.73 seconds / 20ppm for the LSE. The TXCO is 2ppm. How can I calibrate the RTC using TXCO?

[Tesla DeLorean]

With the DISCO you need to change things around to get the TCXO in rather than the 8 MHz from the ST-LINK.

My experience is that BYPASS mode doesn't not work at 32 MHz.

Check the Reference Manual, I think you can measure LSE vs SYSCLK(HSE) on one of the TIM