ADR problem changing from SF7 to SF8

Hello,
i had a problem with the ADR-funktion on LoRaWAN!

The Sensor had no connection to a gateway, after ADR_ACK_LIMIT= 64 + ADR_ACK_DEIAY = 32 attempts (EU868)

the Cubecell changing the broadcasting scheme from SF7 to SF8.
Then three packets are received!

SNR 10.8, 10.5, 10.8
RSSI -130, -132, -130,

After that, no more packets are received!

So what happend there?

E_T

Update:

After ca. 130 (possible) packets two packets arrived with SF9

SNR -11.8, -13.5

RSSI -132, -134

Update 2

Here the new values: Now we are on SF 11 but the signal performance deteriorates (weather-related?)

Nr Name Date/Time SF SNR RSSI Date/Time
835 mk-cc19-hdc1080 2021-05-23T08:39:31.507900Z 7 -6,5 -126 23.5.21 8:38
836 mk-cc19-hdc1080 2021-05-23T08:39:42.789093Z 7 -6,2 -125 23.5.21 8:38
843 mk-cc19-hdc1080 2021-05-23T08:49:43.612780Z 7 -6,5 -126 23.5.21 8:49
850 mk-cc19-hdc1080 2021-05-23T08:59:44.892476Z 7 -4,5 -124 23.5.21 8:59
874 mk-cc19-hdc1080 2021-05-23T09:39:47.142414Z 7 -9 -129 23.5.21 9:39
886 mk-cc19-hdc1080 2021-05-23T10:09:49.530985Z 7 -6,8 -128 23.5.21 10:09
1281 mk-cc19-hdc1080 2021-05-24T01:30:32.330426Z 8 -10,5 -130 24.5.21 1:29
1312 mk-cc19-hdc1080 2021-05-24T02:30:40.984603Z 8 -12 -132 24.5.21 2:29
1327 mk-cc19-hdc1080 2021-05-24T03:00:45.013562Z 8 -11,5 -132 24.5.21 3:00
1432 mk-cc19-hdc1080 2021-05-24T06:41:12.477539Z 9 -12 -133 24.5.21 6:40
2044 mk-cc19-hdc1080 2021-05-25T01:32:16.505670Z 8 -12 -131 25.5.21 1:31
2158 mk-cc19-hdc1080 2021-05-25T04:31:38.337588Z 9 -12,5 -134 25.5.21 4:31
2176 mk-cc19-hdc1080 2021-05-25T05:01:42.483625Z 9 -12,2 -132 25.5.21 5:01
2852 mk-cc19-hdc1080 2021-05-25T21:12:35.833133Z 8 -10,8 -130 25.5.21 21:12
2862 mk-cc19-hdc1080 2021-05-25T21:22:37.370869Z 8 -10,5 -132 25.5.21 21:22
2872 mk-cc19-hdc1080 2021-05-25T21:32:38.274668Z 8 -10,8 -130 25.5.21 21:32
3708 mk-cc19-hdc1080 2021-05-26T19:04:17.008659Z 9 -11,8 -132 26.5.21 19:03
3715 mk-cc19-hdc1080 2021-05-26T19:14:17.384513Z 9 -13,5 -134 26.5.21 19:13
3819 mk-cc19-hdc1080 2021-05-26T22:04:35.778340Z 9 -13,2 -133 26.5.21 22:03
3842 mk-cc19-hdc1080 2021-05-26T22:34:40.840229Z 9 -13,2 -133 26.5.21 22:34
3880 mk-cc19-hdc1080 2021-05-26T23:34:45.760106Z 9 -13 -131 26.5.21 23:34
3912 mk-cc19-hdc1080 2021-05-27T00:24:51.674120Z 10 -14,2 -134 27.5.21 0:24
3921 mk-cc19-hdc1080 2021-05-27T00:34:53.802190Z 11 -15,8 -135 27.5.21 0:34