ISO: How do I avoid watery pasta sauce when serving

I make a 4 day slow cooker pasta sauce from our own stewed Roma tomatoes, lightly seasoned with salt and sugar at canning time. To my 4 quarts of tomatoes, I add 1-2 carrots, 3-4 stalks celery, small pack of fresh spinach, onion, mushrooms if I have any at the time, and a beef bone. This stays on low all day, refrigerate at night, and again low all next day. I remove the beef bone, and boat motor (immersion) the whole thing. I then add 1-2 large cans of tomato paste and italian seasonings. Halfway through the day, I taste and add beef bovril concentrate, worcestershire sauce, oyster sauce and Kraft parm cheese, about 1/4 cup. Day four after it simmers on low again, I then bag it in Ziplocs, squeeze air out and lay flat in the freezer. To use, I remove from the bag while frozen, breakiung it up on the edge of the counter, so you get it all out as opposed to trying to scrape it all out when thawed. I warm the sauce in a pot, and add cooked ground beef, and/or meatballs.

My problem is, when serving, the sauce on the plate is slightly watery. How do I avoid this? Thank you