The current test version should not overwrite your settings of your previous version. It should only have the new option that limits the max amount articles to 1000 (default value), or you could increase that to some big number.
When an NZB is DMCA-ed (mainly all articles gone), propagating (all articles missing after a certain point) or out of retention (all articles gone), a low number / % would be sufficient. I am not really familiar with NZBs missing a lot of random articles, or what % is than the best amount to check. Most usenet providers promote with like 99% or more completeness on their servers, so I guess the amount of failures when checking like 10% (each Xth article) should in general be enough. Maybe some others can also drop their experience with the script.
The script does not check if the PAR files are available, so if say max failure ratio is 10%, and 5% of the articles fails, and more than 50% of the PAR blocks are missing, the download would still fail, even though the script checked ok. Maybe this was the case for your failed downloads?
Note that checking if the PAR files are OK is not simply checking the amount of articles. If I understand correctly how PAR files work, a single missing article in each PAR file would make a repair action almost certainly fail, while just maybe less than 5% of the PAR articles are missing. This makes checking of PAR files a bit more complicated than the RAR check currently in the script.
@Crowley, you have a PM