How long are the door straps supposed to last? I bought two door checks about 6 months ago from partsshop and put them in. And now one of them is completely broken. And the other door is squeeking really really loudly, and the door wont open all the way. It will get stuck closing too and i will have to force it closed. Were they defective? How long do they last? Am I supposed to put more greese on them on top of how they came? Did I do something wrong? thanks.

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1989 260E
- 300E engine
1998 C230
1995 E320