Frameshift mutations can be very severe. what is one reason why they are often so serious?

Frameshift mutations can be very severe. The one reason why they are often so serious is because when a frameshift mutation occurs, it causes changes in many bases downstream and can affect many of the amino acids in the protein.
Basically, a framshift mutation causes changes in the genetic material, codons, and proteins, which can lead to many complications and disorders, some of which are the Tay-Sachs disease, but it can also cause a person to be more prone to certain cancers.