Pre-print servers: Authors using wrong parametrisation to avoid reproducibility before publishing?
I would not assume that this was intentionally done to mislead other researchers. If they wanted to keep their paper confidential, they would not upload it to ArXiv with incorrect parameters. As you have already shown, people are able to find a valid set of parameters by theirselves.

Please consider also the following possible reasons:


The wrong parameters were accidentally put into the paper. One may have forgotten to update the parameters in the paper and left in some placeholders.
You overlooked some important fact, e.g., scaling of parameters. So the error might also be on your side or the corresponding section of the paper is difficult to understand.
The parameters might only work under certain conditions, thus, the authors might be at error.


However, I would recommend to contact the authors using a short and friendly email. You should not assume an error on their side from the beginning as this might come across as rude. You may rather formulate this as a question, e.g., whether they have an idea why you are not able to reproduce the results.
You might either be able to see your own error or help the authors with improving their paper.