Why did the UPI mandate fail even when the IPO was allotted?

After the IPO shares are allocated, technical issues with the bank could result in the UPI mandate failing. The registrar sends the allotment file to the bank, and the funds are deducted as required. However, the shares credited to the demat account can still be traded even if the funds are not deducted. If technical issues prevent the funds from being debited, the bank will make another attempt at a later time.