I have had in the past an instance where combat buildings did no longer work (I noticed it since my 1 shot actions where no longer even close to a 1 shot anymore) It took many many relogs before it was fixed again.
I have no clue what made those combat buildings fail, but I know it is possible for it to happen. and as I cannot reproduce it I havent made a bug report, but it's viable that someone experiences the same thing.
Since in most cases it might not be that obvious it might be this bug that I experienced a while back might happen more often than we know, but it mostly goes unnoticed.
How many of us play manual with 240+% attack boosts and therefore notice it?
I rarely do, except for that specific week where I did and noticed it.
I have had 2 gem tournaments I recorded and 1 of them was considerable easier than the other, but was that ty a failing combat building or just worse luck with enemies / map obstacle combos?
Who could be to blame? this makes a possible bug like this very hard to detect.