This anomaly applies to Revision 1, build codes QFAA-Ax0, QCAA-Ax0, CAAA-Ax0.
The LFCLK RC oscillator frequency can have a frequency error of up to -25 to +40% after reset. A +/- 2% error is stated in the Product Specification.
Always.
The LFCLK RC oscillator frequency is inaccurate.
Calibrate the LFCLK RC oscillator before its first use after a reset.