Electronic – PWM over DMA on STM32F100 behaves strange

Well, there are a couple of solutions for this, basically you need to reconfigure the module and the DMA and make sure that the necessary bits are set, another way is to just DeInit the hardware module (SPI, UART, whatever), DeInit the DMA and finally configure everything like it was the first time

Local structs should be initialised, otherwise some fields can get unpredictable values:

GPIO_InitTypeDef    GPIO_InitStructure={};
NVIC_InitTypeDef    NVIC_InitStructure={};
USART_InitTypeDef   USART_InitStructure={};
USART_ClockInitTypeDef USART_ClockInitStructure={};

mCSP_USART3_RTS_PIN_GO; What does this statement do? Is it a macro or what?

These flags should be declared volatile, otherwise you can get different behaviour at different optimization settings:

while(  (uart3_tx_flg                           == 0)   &&
#if(UART3_TX_FLOW_CTS_EN    == 1)
    (mCSP_USART3_CTS_READ                   == 0)   &&
#endif
    (st_uart3_tx_glb.timeout_timer_u16      >  0)   );