When I add fresh fruit to quick breads, they are gummy in the middle.

Already great comments and suggestions here- do check what size loaf pan you’re using too. Large size ones that are 9” x 5” or using a recipe that overfills a regular loaf pan with aggrevate your moisture problems. Better to do a smaller/shorter loaf.

Also- i’ve had great success using freeze dried fruit in quick breads, i buy freeze dried blueberries and raspberries at trader joes (for a good price) and they “rehydrate” in the bread as baking.

Aside from the comments made by other users, such as adjusting for moisture, I cannot stress enough how important an instant-read thermometer is when cooking anything. The old crumb-free knife and hollow tapping are all well and good, but using a thermometer will tell you exactly when something is cooked. For quickbreads, 180 to 190 degrees Fahrenheit indicates that the bread is completely cooked throughout.

I like to use dried fruit...cranberries, chopped apricots, dates, raisins.
I do use apples but make sure they are diced and patted dry.

The challenge with baking with fruit is overcoming the juices that will release during the baking process. Quick breads also contain a lot of fat as a rule, which helps keep them moist. So adding fruit will also add extra moisture. When you add fresh fruit, it really needs to be patted dry as you can. It also helps if you cut the fruit into smaller bits. Frozen fruit will release a lot of liquid, as the freezing process causes the cells to rupture and as soon as it heats up that liquid gets released into your batter. Some ways to combat this are to chop or cut the fruit into smaller bits, and to coat the fruit in a light dusting of flour- or cocoa if it's going into a chocolate bread. That helps absorb the extra moisture the fruit releases in baking, so you are less likely to have the boggy spots. Also baking a quick bread in a loaf pan generally means the top is going to bake and look done long before the center is baked done. It helps to cover the bread with foil, so the top doesn't end up looking extra crispy by the time the rest of the loaf is baked. I don't test quick breads with a knife, I use a toothpick or skewer or a thermometer. Insert the thermometer into the center of the loaf, and look for it to be between 200 and 210F. One other thing I do if I'm working with extra juicy fresh fruit is to draw out some of the juice by tossing it in a bit of the sugar and letting it sit in a strainer set over a bowl while I prep the rest of the ingredients. Those drained away juices can then be used to make a drizzle for the finished bread, or even brushed over it while the bread cools to add in the extra flavor.

Nope. Haven't had it happen.
Without a recipe, can't identify cause for sure.
Guess it has something to do with either proportions within the recipe or pan used (too small for heat or length of baking).
Here is a recipe from Nancy Clark which always works, with fresh or dried fruit, or other additions.
https://food52.com/recipes/70645-a-to-z-loaf-or-layer-cake
See if that works for you.
And/or compare its proportions to those of your recipe.