As a matter of fact, I am quite sure you have parking sensor problems because of the towbar.
An original (Westfalia) towbar, has holes in it to let the very long sensors through.
View attachment 54721
"old" parking sensor
View attachment 54722
original towbar (note the hole above the hook)
View attachment 54723
non original towbar lacks holes for the long sensors.
My guess is that at least 1 of the 2 middle will be damaged because of the non original towbar.
That is why I opted to spend €50 more on an original towbar instead of a non original towbar.
A parking sensor will be around €100 per piece.
So, the best thing would be to get rid of that rusty piece of metal, and replace with either an original towbar, but as you are mentioning you don't want it, get it taken out, but don't forget to mount an original metal bumper behind the plastic bumper.
View attachment 54724
part 7, and of course a couple of 29 (8? bolts I guess)
View attachment 54725
View attachment 54726
take 7E0807305D and 8x N 0195308.
I hope you are a bit wiser now?
Without the metal bumper, I wouldn't risk to drive around.
And of course, 1 or 2 new parking sensors and wire repair.