This is a primarily user-driven forum, if you want direct support you have to contact ST directly.
> TIM2/TIM3/TIM8 are slaves;
In which mode is the slave controller set (TIM2_SMCR.SMS)?
The initial value of TIM2 output depends on the exact mode you set it, and if it is in PWM or TOGGLE mode, also on whether the counter runs or not and whether the event causing low-high transition (i.e. Compare or Update, depending on the mode and ARR/CCRx value) is reached soon after the counter is run.
JW
