[Some backside story btw]
Ilya aka x4fab (cheers!) changed the shader (the program) for that effect after CSP 1.65 release, to a less-forgiving one, so you can observe such leftovers on quite a few cars when using csp 1.66.2 & 1.67.1 .
Fix requires wipers to be redone [more or less work - it depends] or to use a patch on a CSP

[it's like patching a patch

] to enable 1.65-style wipers "logic" in 1.67.1.
After applying the patch on the 1.67 , the windshield looks and behaves like in 1.65, but you preserve the rain physics and all other new features in 1.67. - kinda compromise on best of the two worlds.
[Of course i cannot upload that patch for patching CSP rain, because rain previews are $$$ feature on the patreon. (But they could have been released free now, if only ... :/ )]
... Or you need wipers redone as i mentioned earlier(in the longer perspective that is the only correct fix, not a workaround)