Yep, you are correct. My first suspect is the key interlock cable is out of adjustment. This requires the removal of the floor console which is the most work. LOL Adjustment is simple.
First, if you look at the first two pics below, I included the key interlock cable adjustment procedure. If you notice, there is one nut that holds the cable in place. If the cable slips under that retainer, what you are experiencing will result. So, it will be a matter of loosening that nut, pushing the cable back into the correct position, and then retightening. The directions explain the process step by step and include pics to help you identify the components.
Next, the first thing you need to do is remove the floor console. It's really not hard to do but can be a bit of a pain. The bezel around the shifter will be held in with clips.
I went through my manuals, and for some reason, they don't provide directions. However, I checked online and was able to find a few pics that show where the main bolts on the console are located. These will need to be removed. Additionally, there will likely be a plastic push-in cover over the bolts.
Once that is removed, perform the adjustments in pic 1 and 2. Note: The adjustment below are specific to your vehicle. The pics are general from a Mitsubishi Galant.
Let me know if you have questions.
See pics below. Note: in most cases, there will be nuts on the opposite sides of the console in the same positions as what is circled.
Images (Click to make bigger)
Saturday, January 22nd, 2022 AT 3:37 PM