I'm not a judge but I am a professional journalist and reviewer and it was clear to me when reading the spreadsheet comments, based on feedback entrants had given on the game pages as well as what I experienced in playing some of the games, that you were rushing through the entries (presumably to meet the travel deadline) and were missing some things and/or experiencing bugs that others weren't and I felt bad for the developers who were negatively affected by this.
You are the judges and prize givers, so what happens in your competition is up to you, but these are your choices:
1) You play a game once and that's it - if you miss something or there's a bug that randomly manifests then it's just bad luck for the developer.
2) You load/play a game more than once, especially if something seems odd, to make sure you didn't just hit a rare bad instance of a game. You also take note of what people are saying in the comments on the game pages to make sure that your experience aligned with theirs. This is, after all, a jam. Weird stuff happens and developers often don't have time to do much polish. [FWIW, this option is my preference.]
Neither point is right or wrong and both have pros and cons (and set a tone that indicates the kind of developer you would prefer to see succeed) so it's up to you to pick whatever works for you. You just need to make the rule/procedure very clear in the official rules.
Some other points to consider:
* Some jams offer a post-jam window (although I don't know if that's generally done, or can be set as an option, on itch) to give developers a little bit of leeway to kill last-minute bugs and, more important, to upload in case of an Internet meltdown, which can happen in some countries with dodgy Internet connections or electricity supplies. Some will have a cutoff time but allow for a "post-jam-fix" build to be uploaded as an additional file within a small time frame, if a game breaking bug does manifest, so that the judges can at least see the intention behind the game. (I don't know that that's necessary here; it's more useful for competitions that have multiple categories - so the bug might take the game out of technical contention but it would still be eligible for the art or sound prize.)