It sounds like you're pretty close to getting this simulation working smoothly, nice effort so far! When garments explode during simulation, it's often down to one of a few common culprits. Since you've already tried adjusting the fabric type (spandex vs cotton), it might be worth double-checking the following:
Normals and Panel Orientation: After rotating the back panel 180 degrees, ensure the normals are still facing outward and not inverted. Cloth simulations can behave erratically if panels are flipped inside-out.
Seam Alignment: Even a tiny misalignment in the seams can cause panels to pull in unpredictable directions. Try zooming in and verifying that all seam lines are properly matched and not overlapping awkwardly.
Scale and Gravity Settings: Double-check the unit scale in your scene. If the garment is too large or too small relative to the avatar, gravity and cloth weight won’t behave correctly. Also, confirm that the gravity value in the simulation matches real-world conditions unless you're going for a stylised effect.
Collision Offset and Layering: In 3ds Max, the Cloth modifier has settings for collision offset and object thickness. If these are too low or panels are too close together, the simulation might treat them as intersecting, causing the “explosion” effect.
If you’re experimenting with more fitted or structured garments, you might find inspiration in how high-end loungewear is constructed in real life. Click here to see a good example of how layered quilted cotton behaves, something like this could help you visualise panel flow and weight distribution when simulating cotton-based fabrics.
If you're able to share the scene file, as someone else mentioned, that would definitely help others give more precise advice. In the meantime, keep tweaking cloth sims are notoriously fiddly, but extremely satisfying once they work!