Ordinal response with monotonic predictor

Interfaces brms
8

The problem is I do not get the similar pattern as you wrote:
The response is as blow:

 p$prior[1]
[1] ""
> p$prior[3] 
[1] "student_t(3, 0, 10)"
> p$prior[1] 
[1] ""
> p$prior[3] 
[1] "student_t(3, 0, 10)"
> p$prior[18]
[1] "student_t(3, 0, 10)"
> p$prior[21] 
[1] ""

:(
I can send some of the data, if it helps to understand why!