During the Shonen Jump of July 5th-6th of 2008, a Shonen Jump was ran with many Mantis errors. July 6th started off well until we got to a certain round massive amounts of players were dropped. I concluded it was my fault for entering the wrong drops. But I was probably wrong. On July 7th we had a Yu-Gi-Oh! regionals running for 8 rounds. First few rounds were awesome and smooth. I then had to assign a seat to a certain player due to personal issues. He was seated at table ***. As the rounds went on people dropped and we ended up with 98 tables plus the table at ***. WE enter results in for round 6 and when we typed in *** mantis would bug out and bring us back to table one. So we were not able to change results in that certain table and had to switch those players out and put them in another table. After we switched them in the system using manual pairing we had another problem occur. The players at table *** were cloned and then replaced two other players. We solved the issue finally with a huge delay. We go to round 7 and then to 8. Pairings went up for round 8 and a lot of people were playing the same opponents as last round, but not all. We tried re-pairing the round and the results for the same. I remember changing a result at a certain round and then manually moving their opponents. But when we loaded up round 8 the results were changed back into the default (before a changed the results for a previous round and then re-pairing those players manually). Mantis really needs and upgrade and all these bugs should be checked. Especially running big events like Shonen Jump, we need a program that's at tip top shape and shouldn't bug out like this. Thanks.