iOS BLE disconnect repeatedly wuth connection has timed out unexpectedly

[HinnaX]

Hey,
since iOS version 18.6.2 the BLE connect to our BLE peripherial with nrf52840 getting disconnect events.
Also the range between them is very bad.
The connection parameter are set with these values

CONFIG_BT_PERIPHERAL_PREF_MIN_INT=12

CONFIG_BT_PERIPHERAL_PREF_MAX_INT=12

CONFIG_BT_PERIPHERAL_PREF_LATENCY=3

CONFIG_BT_PERIPHERAL_PREF_TIMEOUT=200

These are conform the apple connection parameter quidelines

developer.apple.com/.../_index.html

Can anybody help?

[Benjamin]

Hi Hinnerk,
Does the issue happen on multiple iOS devices and only 18.6.2?
Could you provide a sniffer trace?

Best regards,
Benjamin

[HinnaX]

Hey Benjamin,
thanks for your reply. Yes it happens on multiple iOS devices with these iOS version.
Unfortunately I can't provide a sniffer trace. 
I see that the rssi value is very bad. After 3-5 meters these value is -85dBm to -90 dBm.
Now I try to increment the TX Power. This improves the rssi value to -75dBm.
Are there any option to improve the connection.