My first films with Xtol got bubbles. I didn't use a water pre-soak, because I think I read where Kodak didn't recommend it for this film.(posted 8885 days ago)I had this problem many years ago with Plus-X in 120.
So here's what I suggest.
1. Use an initial water pre-soak. Make sure the water is the same temperature as the developer, and run it for 1 to 2 minutes. The emulsion absorbs the water, and wets it. It reduces the chance for air bubbles to cling to the film. Dump the water and drain. By the way, this also helps disolve the anti-halation backing and dyes, so don't be surprised if the water is colored when it comes out.
Note that this reduces the development slightly, but I've not found it to be of any consequence. And those air bubbles ruin the negative.
2. Don't use an acid stop bath. Use a plain water bath instead. Running water is the best, but impractical for most tank processing. Use 2 or 3 exchanges of water. Again, make it the same temperature as the developer.
3. Use an alkaline fixer. Photographer's Formulary TF4. This keeps the whole process alkaline, and prevents gas bubbles from "erupting" in the emulsion. In addition, TF-4 has great capacity, doesn't smell, fixes fast, and washes out easier than acid based fixers.
Actually, 1 & 2 will probably solve your problem. But TF-4 is so great, I had to put in the plug.