Hello. Using the shifter knob on my 1987 300SDL got very soft very recently. It felt regular one day, then the next day moving between gears is much less resistance, it feels kind of fluid. Going into reverse I've heard some grinding a couple times, rather than than the quick lock. There's a hollow thunk noise that happens when switching now, that doesn't seem quite like it used to. I've attached a video of changing gears that shows off this sound (edit: only while the car is off at the moment. I'll try to add some with the car)
https://www.youtube.com/watch?v=eSbSW09xKS8

The other gotcha is that I have to shake around the shift knob to get the car to start in park. In neutral, the car detects that it's in a good position to start, but park is much more finnicky all of a sudden.

Does anyone have ideas what may have gone wrong, or ideas for how to diagnose this? I haven't noticed any big changes in shifting, but the grinding going into reverse, the hollow thunk sound when using the shift knob, and the loss of starting while in park make me feel like something has gone amiss, & I'd like to know what the story is.

Thanks!