@xarmoda, interesting. -89 dBm is borderline. -100 it’s amazing your phone was able to detect that at all.
Probably a huge PITA, but you could experiment with temporarily locating your RPi somewhere optimal.
Another line of enquiry to follow:
In your bluetooth adapter device:
Hit the download diagnostics button:
Within, you can search for what devices your bluetooth adapter has discovered:
"discovered_devices_and_advertisement_data": [
{
"name": "POOL01",
"address": "EF:1B:FD:4A:38:44",
"rssi": -85,
"advertisement_data": [
"POOL01",
{
"1095": {
"__type": "<class 'bytes'>",
"repr": "b'\\x01\\x04\\x00\\x01\\x00\\x00\\xaa\\x10QK\\x8c\\xd8\\xb0e\\x05\\t\\x01\\x02\\x02\\x00'"
}
},
{},
[
"45000001-98b7-4e29-a03f-160174643001"
],
-127,
-85,
[]