I'm glad she's hanging in there.
It does sound like the crop is slow and perhaps she has some blockage, whether that's from inflammation in the body from something reproductive or she has some type of fibrous material that is impacting the system it would be hard to know.
Giving the coconut...
Welcome To BYC
Where are you located in the world?
How old is this hen?
How long has this been going on?
Was/is she laying eggs? You mention she was given Lucrin, so is this to stop her from laying eggs?
Has she had trouble with production in the past or had signs of Salpingitis, etc.?
If...