Am I right to understand that at SF7, 8 and 9 you don’t receive anything at all, and at SF10 you’re missing some packets?
If so, then @jreiss already answered about the problems at SF10.
Regarding SF7, 8 and 9: the higher the SF, the longer the airtime and the better the reception/maximum distance. So, to use a lower (better) SF you need to be improve the reception. Like be closer to the gateway, put your gateway and/or node in a higher position, and so on. See Best position for a gateway.