The effect of tack in shows

I'm just wondering if tack has any effect at all in how a horse performs in shows? Does it matter at all if a horse has 5/5 tack or 1/5 tack when entering shows?

Several of my horses with 5/5 tack have been losing in shows to same level horses with lower level tack. Or have been losing to lower level horses with same-ish level tack.

The presence of tack definitely does have an affect on show results... if you look at this record and compare the results on the first page to those on the second. It's obvious when I realised he didn't have tack on.

That doesn't say anything about the different grades of tack, of course.

5/5 tack definitely gives you a distinct edge on the competition when it comes to showing.  Equipping tack adds stats to your horse without bumping it up to another showing level.  The more upgraded the tack, the more extra stats you get.  These are the numbers in green to the right of your regular stat numbers.

However, a horse fully equipped with 5/5 tack can still be beaten by a horse that does not have fully upgraded tack because tack is not the only thing that affects showing.  If your horse has lower stats in the two traits that are associated with the horse's specialty (such as endurance and strength for Driving, or speed and agility for Show Jumping) it can be beaten by a horse with higher stats in those traits.  Also, training levels play a part.  Every horse, no matter how high their stats, can have good days and bad days in showing.  Sometimes you just have bad luck, or someone else may have good luck, and you may be beaten even though your horse appears to be the better horse.  Training levels affect how good your luck will be.  A training level 5 will have better luck than a training level 1.

So, yes, you will do much better in showing if you fully equip your horse with 5/5 tack, but it will not guarantee that you win every show.  Even if your horse appears to be perfect in every way, it will still occasionally lose.

If there is a bug in play, that is an entirely different issue.  You will still be in a better position to win if you have fully upgraded tack.