If you setServices using strings for BLE service / characteristic UUIDs on an ESP32 you will get errors.

For example, with 2v04:

>NRF.setServices({
:  "BCDE" : {
:    "ABCD" : {
:      value : "Hello",
:      readable : true
:    }
:  }
:});
ERROR: empty UUID type
ERROR: empty UUID type
=undefined

This results in the service being advertised, but under the wrong UUIDs. For me, instead of being advertised under the service 0xBCDE, I see 80084259-FFFF-FFFD-0000-00003FFC0000 and instead of the characteristic 0xABCD, I see 0xFEBC.

Note that if instead you use integer UUIDs, as in the following you get a correct advertisement.

>NRF.setServices({
:  0xBCDE : {
:    0xABCD : {
:      value : "Hello",
:      readable : true
:    }
:  }
:});
=undefined

Note there is a separate issue #1724 on master.