Air stays in the bag
Make sure that the bag is correctly placed in the machine before you start vacuuming. Check that there are no leaks: empty the bag of air and submerge it under water. If bubbles escape, the bag must be changed. If you are using a custom-made bag, check the closure. If it is creased, it indicates a leak. Open the bag and close it again. Do not try to make your own side closures, they may leak and let air escape
The air escaped from the bag and entered again
Check the closing system of the bag. If it is crumpled, it may cause air leakage. Open the bag and close it again. Sometimes moisture or food residues (grease, sauce, juice, etc.) may remain on the closure system and prevent the packaging from closing properly. Open the bag and close it again. If you are packaging sharp food, the bag may be punctured, cover the food with a material to protect the bag (e.g. absorbent paper). Pack again. If it is difficult to obtain correct vacuum packaging, the food may spoil, if this is the case, do not eat it.
The bag is melting
If the bag melts, the welding rail is probably too hot, wait 40 seconds to let the device cool down between each use.