as Darcy said, take the door panel off, the "door control" that the inside door handle fits on is a pretty simple device and has a spring in it. I bet that spring is broken. You can take the door panel off in probably 10-15 minutes and back together in the same amount of time. You will probably end up just buying the door control and a new door handle (splines in the door handle can wear, I like to replace the handle when I replace the remote, unless it is perfect inside. Below is a link to the driver side one.

https://www.americanclassic.com/1955-59-Door-Control-Left/productinfo/18%2D827/


Mike
1955 Chevy 6400 ex-flatbed (no bed now!) sold September 2023
In the Stovebolt Gallery
1958 Chevy 6400 flatbed W/dump
In the Stovebolt Gallery
1959 Chevy Suburban Owned for almost 20 years, Daily Driver -- sold May 2016
In the Stovebolt Gallery

Sufficient unto the day is the evil thereof