No. This appears to be a check altering/posting error. The credit union must correct it. You should notify your credit union so it can investigate the error. The credit union may require you to complete an affidavit.
The time period for this prompt notification may vary by credit union and state; if a check was altered, you may have up to one year to assert one alteration. Generally, for multiple alterations, credit unions require you to notify them of any error(s) within 30 days after you receive the statement.
Your account agreement specifies your credit union's specific time requirement. Review that agreement, and then contact the credit union directly regarding any alleged error.