We aren't quite sure how qualities for shows have become so complicated to understand. We have several theories, but all of that is coming to an end.
First, the feature Archive on first match was poorly named, and caused it to be confused with and intertwined with the Archived Episode Status episode status over time.
Archived Status is only meant to be for episodes that we know we have but SickChill does not have a location for, or it does not exist at the location.
Archive on first match is a relic from the time when SickChill only had one quality list, back in SB days (afaik), where you needed to specify if you wanted to keep looking until the best quality in that single list was reached.
With the use of two quality lists like we have for custom qualities, Archive on first match can be eliminated. This removes the continued confusion which caused users to mentally link Archive on first match and Archived Status, which are two totally separate features. It also greatly simplifies the code, and allows us to prepare for better quality handling and eventually user order-able quality lists ("CP Style"). It also makes it easier to add the 2k/4k/UHD qualities.
Well, if you had your qualities set up in an odd custom configuration, SickChill might think it needs to re-download something that you think it should not.
The solution is simply to change the quality settings for your shows.
If you have qualities in the Preferred list set, any episode matching a quality in this list will not be replaced with a better quality. AKA it is a "best" match and is final.
If you ONLY have qualities in the Allowed list (Or have a preset selected other than custom) it will also stop on the first match in this list and be considered a "best" match, and never be replaced with a better quality.
If you have qualities in BOTH lists, it will accept any quality in the Allowed list, and continue looking for a better quality in the Allowed list, until it finds one in the Preferred list.