Excessive "stagnation" execution time using slice sampler with one HalfFlat prior

I have a model that contains 5 parameters. let me describe my motivation and later the problem I am facing.

  1. One model parameter has a non-informative prior, I used pm.HalfFlat() because the parameter is practically un-identifiable… I want to obtain a proper posterior. In the past I’ve been using pm.Uniform() but the posterior was always very similar to the prior.

  2. The execution gets stagnated exactly at the half… See the next terminal outputs.

Sampling 4 chains, 0 divergences: 50%|████████████████████████████████████████████████████████████ | 202001/404000 [3:51:12<6:39:55, 8.42draws/s]

Sampling 4 chains, 0 divergences: 50%|███████████████████████████████████████████████████████████████ | 22000/44000 [22:30<37:57, 9.66draws/s]

Even changing (reducing) the number of samples I get this problem. Any advice will be helpful…