Can’t say until I see your logs. It’s possible, if they are all recorded from the same source/tuner and if it’s creating corrupted files they may all fail for the same reason. Again the log files will tell you why, you can open then and look for the error or see the conversion history page and it’ll tell you the reason for the failure also.
You mentioned that it’s been working fine for a year. So try to trace back what changed, a windows update? A driver update? Firmware update?
You can find instruction to upload files to the server here: