New Delhi: The Central Board of Secondary Education (CBSE) detected around 20 cases of manipulation in answer sheets during the first-time implementation of its on-screen marking (OSM) system this year, while over 13,000 answer sheets ultimately had to be evaluated manually due to scanning quality issues, government sources told PTI on Friday.The matter came to light when students looked at the scanned copies of their answer sheets uploaded on the CBSE portal and found that some were not theirs.“There was a case of Vedant. Vedant got the answer sheet and was horrified to see that it was not his answer sheet. There was a glitch in the scanning. There was also a girl named Sanjana there,” sources told PTI.Class 12 student Vedant had earlier gone viral on social media alleging that the Physics answer sheet uploaded by CBSE during the revaluation process was not his. Many other students, including Sanjana, also reported similar issues online.CBSE later contacted the students and shared the correct answer sheets. The board said that matters related to mismatched answer sheets and other concerns in the revaluation process are being handled on “top priority”.“In some cases, there were irregularities in scanning. There are around 20 such cases. This was pointed out by the students after seeing their answer sheets,” sources said.According to sources, more than 98 lakh answer sheets comprising about 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 re-scanned. Ultimately, a little over 13,000 copies did not achieve the required legibility quality even after re-scanning,” sources told PTI.The controversy over the digital assessment system has forced CBSE to postpone the opening of its Class 12 result post-verification and revaluation portal from May 29 to June 1.In a post on X, CBSE said the portal is being strengthened to ensure a “transparent, smooth and error-free process” for students applying for verification of marks, photocopies of answer sheets and revaluation services.A CBSE official said the website infrastructure is still being upgraded to avoid disruptions during the application process after many students reported technical glitches while accessing the post-result services.Students and parents had raised issues ranging from difficulty in accessing scanned copies of evaluated answer sheets to payment gateway failures and incorrect fee display on the portal.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 anomalies in the digital assessment system and assured students that corrective measures will be taken.The Board has advised students not to panic and use the official support channels for assistance regarding verification and revaluation services.CBSE expects huge traffic on the portal, lakhs of students can apply for post-result services. Reports suggest that more than four lakh applications for scanned copies of answer sheets had already been received.Officials defended the rollout of OSM, saying the technology-driven assessment improves transparency and allows answer sheets to be shared with students digitally.“Technology is the future. From next year, answer sheets will also be available in DigiLocker along with marksheets,” sources said.“From next year, all the answer sheets will be sent together on DigiLocker. Technology gives you a certain kind of transparency, which is not possible otherwise,” he said.“Whenever you do something for the first time, there are challenges,” sources said.Sources further said that Koempt and Tata Consultancy Services (TCS) had technically qualified in the final round of bidding for the project, with Koempt emerging as the lowest bidder.“When the financial bids were opened, Coempt had bid around Rs 24.75 per answer sheet including taxes, while TCS had bid around Rs 65-66 without taxes,” sources said.The contract has come under political scrutiny after Congress leader Rahul Gandhi alleged that Koempt, earlier known as Globarena, had a controversial past in Telangana. He has demanded an independent judicial investigation and SIT investigation into this matter.