Replace "prevent" with something weaker

I have this sentence.

Method A prevents the model from reaching a poor solution.

but I am trying to replace the word prevent with something "weaker" because method A does not prevent the model from reaching a poor solution, it just makes it harder for the model to reach that poor solution. However, I am not sure if the sentence below is grammatically correct.

Method A makes it harder for the model from reaching a poor solution.

Forgive my English its not good.

The verbs "to hamper", "to hinder" do not imply a total stop to the process represented by their object and so would suit fairly well the purpose. As well, "to impede", provided the context is clear, does not imply a total stop.

A slight modification is necessary, though.

• Method A hinders the model in its reaching a poor solution.

If you rewrite it the way you suggested with the word "harder" you would need to do some editing at the end of your sentence.

I recommend: Method A makes it harder for the model to reach a poor solution.

Another option might be restructuring the sentence but it might be more awkward to read.

The model is less likely to reach a poor solution with Method A.

As another answer mentioned, your second sentence would be more properly rephrased as:

Method A makes it harder for the model to reach a poor solution.

However, it appears that you are describing the expected outcome of a modeling process. If so, it sounds more natural to talk about the probability of the outcome. For example:

Method A reduces the likelihood of the model reaching a poor solution.