Immediately after reading the time from the RTC using HAL_RTC_GET_TIME RTC clock stops. Changes only position Subsecounds. The second problem is that when you first start debugging is successful but the stay and want to restart it stops at Reset_Handler:
ldr sp = _estack / * set stack pointer * /
only helps clear the memory of the processor with ST-LINK utility.
My workbench :
Eclipse Mars 2