Also a new pedalboard, uncomfortable bench position, wrong organist shoes, practice experience, inefficient practice techniques, and pedal preparation all have something to do with the amount of mistakes you make when playing with your feet.
But there is another even more important factor at work here. It's much more difficult to spot, though. Here it is:
Pedal mistakes are also triggered by the insufficient ear training. Let me explain.
You see, when you make a mistake in the pedals, your ear has to do two things very quickly, actually instantly:
1. Recognize that this is a wrong note.
2. Recognize what kind of note you just hit.
The 1st point is very clear - if you know the piece well, any wrong note is quite obvious and needs fixing (unless you sight-read). The 2nd point though is much more subtle - you can't fix the wrong note unless you know what this note exactly is. You can't play the right note after you hit the wrong one unless you know your target note and the exact location of the wrong note.
This is where ear training actually comes in. If you can guess which exact note you are playing with your feet (not by looking but by listening only, perhaps with your eyes shut), then you can easily know where is the right note (right or left, by the interval of the second, third etc.)
If you work on your ear training and developing perfect pitch, not only your general musicianship and understanding of pieces you are playing will improve but actually your pedal (and manual) performance will as well.
This all makes sense if I look at some of my organ students playing who have a perfect pitch. After learning to play the organ for about 8 months, such students can easily play pieces with advanced double pedal parts easily.