Dictionaries unanimously describe 訳 as an 頭高型 word: わけ{HL}
However, oftentimes when 訳 immediately follows a downstep-type verb, I don't hear any drop at all. That is to say, phrases like なるわけ sound like なるわけ{HLLL} to me. On the other hand, when following a flat-type verb, I think I generally hear it: 寝るわけ = ねるわけ{LHHL}
This is quite reminiscient to me of what happens to the pitch of こと when it follows a downstep-type verb, namely it "loses" its own pitch accent pattern and just stays low (more here).
Is my perception correct? Are なるわけ{HLLL} and ねるわけ{LHHL} the only permissible pitch accent patterns in Standard Japanese?