NEW DELHI: The Central Board of Secondary Education (CBSE) detected around 20 cases of answer-sheet mix-ups during the first-time implementation of its on-screen marking (OSM) system this year, while more than 13,000 answer sheets ultimately had to be evaluated manually due to scanning quality issues, government sources told PTI on Friday.The issue came to light after students accessed scanned copies of their answer sheets uploaded on the CBSE portal and found that some did not belong to them.“There was a case of Vedant. Vedant got the answer sheet, and to his horror, he discovered that this was not his answer sheet. There was a mix-up in scanning. There was a girl called Sanjana too,” sources told PTI.Class 12 student Vedant had earlier gone viral on social media after alleging that the Physics answer sheet uploaded by CBSE during the revaluation process was not his. Several other students, including Sanjana, also reported similar issues online.CBSE later contacted the students and shared the correct answer sheets. The board said cases related to mismatched answer sheets and other concerns in the revaluation process were being handled on “top priority”.“In some cases, there was a mix-up in scanning. Such cases are around 20. Students pointed it out after accessing their answer sheets,” the sources said.According to the sources, more than 98 lakh answer sheets amounting to nearly 40 crore pages were scanned under the OSM system.“Out of these 98 lakh answer sheets, around 68,000 were found to have quality issues during scanning and were rescanned. Eventually, a little over 13,000 copies still did not attain the required legible quality even after rescanning,” the sources told PTI.The controversy over the digital evaluation system has also led CBSE to postpone the opening of its Class 12 post-result verification and re-evaluation portal from May 29 to June 1.In a post on X, CBSE said the portal was being strengthened to ensure a “transparent, smooth and error-free process” for students applying for verification of marks, photocopies of answer books and re-evaluation services.A CBSE official said the website infrastructure was still being upgraded to avoid disruptions during the application process after several students reported technical glitches while accessing post-result services.Students and parents had flagged issues ranging from difficulty accessing scanned copies of evaluated answer books to payment gateway failures and incorrect fee displays on the portal.The concerns intensified after questions were raised over CBSE’s new OSM system introduced for Class 12 evaluation this year. Union education minister Dharmendra Pradhan recently acknowledged discrepancies in the digital evaluation system and assured students that corrective measures would be taken.The board has advised students not to panic and use official support channels for assistance regarding verification and re-evaluation services.CBSE is expecting heavy traffic on the portal, with lakhs of students likely to apply for post-result services. Reports indicate that over four lakh applications had already been received earlier for scanned copies of answer books.Officials defended the rollout of OSM, saying technology-driven evaluation improves transparency and allows answer sheets to be digitally shared with students.“Technology is the future. Next year onwards, answer sheets will also be available in DigiLocker along with mark sheets,” the sources said.“Next year onwards, all the answer sheets would also be sent simultaneously to DigiLocker. Technology gives you a certain kind of transparency, which otherwise is not possible,” they added.“Whenever you do something for the first time, there are challenges,” the sources said.The sources further said that Coempt and Tata Consultancy Services (TCS) had technically qualified in the final round of bidding for the project, with Coempt emerging as the lowest bidder.“When the financial bids were opened, Coempt had quoted approximately Rs 24.75 per answer booklet inclusive of taxes, while TCS had quoted around Rs 65-66 without taxes,” the sources said.The contract has come under political scrutiny after Congress leader Rahul Gandhi alleged that Coempt, formerly known as Globarena, had a controversial past in Telangana. He has demanded an independent judicial probe and an SIT investigation into the matter.