A credit union cannot place a lien on a vehicle once the bankruptcy case is filed, and an attempt by a creditor to collect a debt that was discharged in bankruptcy may expose the creditor to damages, including punitive damages under some circumstances. I suggest contacting an attorney in your area to see about reopening the bankruptcy case and filing for damages against the credit union for their potential violation of 11 USC 362. You may be able to file a Motion for Cause to show the credit union is in contempt of the automatic stay order, or you may have to file an Adversary Proceeding if circumstances warrant.
I do not think it is wise to proceed without an attorney since it appears that the credit union may be using the fact that you are not represented by an attorney to try to kick you around, plus motions of the sort I mentioned require legal experience for the best likelihood of success.
I hope this helps and a positive feedback is always appreciated if this was useful to you.
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