LPTIM wb55 issues with HAL_LPTIM_AutoReloadMatchCallback

Hi community,

I'm having some issues with LPTIM on a WB55 nucleo board.

I have set a LPTIM to fire interrupts every 2us (with a PWM output). It uses PLL as CLK source, and the PWM signal I see in output is effectively correct.

The problem arises when I call HAL_LPTIM_AutoReloadMatchCallback(), in which I simply toggle a pin at the same frequency (500KHz, 2us).

The representation of the signals is here below, where the first graph is the PWM signal and the other is the pin I want to toggle in the callback:

The only line of code inside the callback is HAL_GPIO_TogglePin(A0_GPIO_Port, A0_Pin);

Do some of you know why this happens?

Thanks so much