Seal failure complaints come in fast and vague, "the bags are opening up" or "the seal just isn't holding." Before I touch a seal bar setting, I want to know where the contamination, the settings, or the resin is hiding the problem, because it is almost always one of those three.
Contamination on the seal area
Dust, product residue, oils, or even printing ink that bleeds into the seal zone will keep two layers of film from bonding properly, no matter how good the resin or the equipment is. This is especially common with food and powder products, where fine particulate gets between the film layers right at the point of sealing. If failures are random and do not track with any equipment or material change, check what is actually sitting at the seal interface before you change a single setting.
Wrong temperature, dwell, or pressure combination
Seal strength is not controlled by temperature alone, it is the combination of temperature, dwell time, and pressure working together. Too much heat and not enough pressure can scorch the surface without fully fusing the layers underneath. Plenty of pressure with too little dwell time will not give the resin enough time to flow and bond. I see a lot of operators chase one variable, usually temperature, when the actual fix is in the dwell time or pressure setting instead. Change one variable at a time and give each change a real test, not a guess based on how the seal looks.
Resin selection mismatch
Not every resin seals the same way. Some structures use a sealing layer specifically formulated for hot tack and seal strength, and if that layer was substituted, downgauged, or left out of a structure to save cost, the seal will be the first thing to suffer. If you changed suppliers, changed a resin blend, or moved to a thinner gauge recently and the seal got worse right after, the resin is the first thing I would look at, not the sealing equipment.
The short version
Random, inconsistent failures point to contamination. Failures that change with your settings point to the temperature, dwell, and pressure combination. Failures that started after a material change point to the resin. Work through those three in that order and you will find the cause faster than adjusting the seal bar by feel.