1. Material problem: the loose trunk bag may be caused by poor material. For example, using low-quality cloth or sewing is not firm, which will easily lead to loose trunk bags.

2. Frequency and duration of use: If the trunk bag is used frequently, especially when it is loaded with heavy objects or pressed for a long time, it will also cause the trunk bag to become loose. Long-term use will make the material relax and lose its original compactness.

3. Extended content: In addition to the above reasons, there are other factors that may cause the trunk bag to be loose. For example, the design problem of trunk bag, if the support of heavy objects is not considered or the appropriate structural design is not adopted, it will easily lead to looseness. In addition, incorrect use methods, such as overloading or incorrect loading methods, will also affect the tightness of trunk bags.

To solve the problem of loose luggage, the following methods can be considered:

1. Material replacement: If the trunk bag is loose due to material quality problems, consider replacing it with high-quality materials, such as solid nylon cloth or structurally reinforced materials.

2. Strengthen the structural design: If the design defect of the luggage leads to looseness, consider strengthening the structural design. For example, support rods or reinforcing pads are added at key positions.

3. Correct use and maintenance: The correct use and maintenance of luggage is also an important factor to maintain tightness. Avoiding overload, loading items correctly and cleaning and maintaining luggage regularly can prolong the service life and keep its compactness.

To sum up, the looseness of 23 Juan Lincoln Z trunk bags may be caused by material problems, frequency of use, duration of use and other factors. Solutions include changing materials, strengthening structural design and proper use and maintenance.