Thankfully this was a cake for family only - which by no means mean that it should be less perfect but they are more forgiving and they love all my cakes so they didn't question my baking abilities.
I did a beautiful carrot cake, from a recipe I've used before which came out fabulous the previous time. I baked it even a little lower and longer to ensure its cooked through as I had cut the recipe in half for 6" tins and the first time the outer layer got slightly too brown.
Anyways did the cake test in the over and it came out clean and almost dry so I took the cakes out. All good. Decorated the following day and delivered to restaurant where we were all having dinner. All good.
Cut the cake. Not good.
The cake inside poured out (it was covered fondant and cream cheese frosting), it literally looked like batter in the middle still. I was flabbergasted. Sooooo disapoointed and embarrassed! My mom and sis poke at the cake and see that the top layer looked ok but the bottom didn't look cooked. Thankfully I had done a trio of cakes and the tall chocolate/vanilla one was perfect and everyone enjoyed it.
We took the "raw" cake home, I scraped of all the icings and laid it flat in a pan and put it in the oven, hoping to cook it through enough to at least make use of the cake still and get it edible (it did taste delicious when we tasted the parts that looked cooked). over an hour and still very very wet.
I get home and check the recipe (I tick off ingredients as I go for fairly new recipes) and all ticked so I couldn't figure out what I had done wrong. Then it hit me. Crushed pinapples. I forgot to drain it and the syrup from them must have been what caused all the gooieeness!! And as the cake thawed from the fridge while I was decorating the syrup must have been dripping inside to the bottom of the cake.

What a relief that I had not tried to serve a raw cake (that would have been terrible and a hazard). I'm almost 100% certain it was that, plus the recipe called for a lot of sugar to soak the carrots in, also turned syrupy so maybe it was that. Well I found a new recipe to try or will just omit the pinapples or cut down the next time.

If anyone knows why this happened that would be great to hear - if its not the pinapples like I think it is.

You're probaby right that it was the pineapples if you didn't drain them. That would be way too much liquid!