How can one determine whether the phenomenon of blistering is caused by the silicone sealant itself or by the substrate?

Judgment of the bulging phenomenon:

Firstly, the joint of the curtain wall panel exposed to sunlight shows a large area of unevenness, while the joints not exposed to sunlight are all smooth;

Secondly, by cutting the joint, it can be seen that the uneven joint has fully cured sealant and is solid.

Judgment of the bubbling phenomenon:

Firstly, the surface of the sealant is mostly continuous or single bubble-like protrusions;

Secondly, when cutting the corresponding position of the sealant, it is hollow, and this may exist on the sunny or shady side of the curtain wall.