Due to many further questions/problems here in the thread, I would like to expand the topic to all models of the Synology "+" series and all questions about internal flash memory regarding hardware replacement, image repair, elsewhere with a new topic. Synology model upgrades are also possible here:
As already mentioned, the thread owner also has the opportunity to close this topic here. From my side, thank you @wool very much for the information about the pin-out and the ideas that came from it.