When you have a bubble, you're going to have trouble.
This is the start of what's called "pancaking," where output just collects around the stoma area and doesn't drain to the bottom of the bag, especially after standing.
The next stage is a bubble that will form, growing increasingly larger and putting sideways pressure on one's ring or paste adhesive, and forcing output under it, causing a leak.
Once the output, which contains active bacterial digestive enzymes, hits your skin, it begins eating it, causing skin burn wounds to occur along with some pain.
So although diet and portion control can assist with eliminating pancaking, it still sometimes catches one by surprise, so they need to watch for it before it causes far worse damage.
The remedy is simple: do a dump and pour some water into the bottom of the bag to flush, do it again, and seal up. Go lay on your back and get the water up around the stoma area and gently massage through the bag to loosen the output and clear the stoma. Don't squeeze the bag or try to push the output; that places pressure on the paste or ring just like the pancaking would. Flush and rinse the bag well.
An extra trick is to use just a few drops of antibacterial dish soap to kill the digestive enzymes in there and wash out the bag. The residue soap left over does a good job of eliminating the next future dump odor and cleans the bag as well or else leave a little water and soap in there to mix with the next output.
Now add a little air to the bag by leaving the end open and pulling the two sides of the bag apart to eliminate the vacuum effect. An effective method is to have a flat coffee stir stick or tongue depressor and insert it into the bag which then you can separate the two stuck together pieces of plastic. Once wide enough, close the end to trap the air and gently roll the bag up, thus forcing the air to the top of the bag and around the stoma. The bottom will cling together some to keep the bubble of air near the top.
Check your diet that you're not eating too many liquid-absorbing type foods like crackers, dry bread, and cookies without sufficiently mixing enough water with it in each mouthful.