Your server either does not allocate enough memory to PHP to clean all 2,881 files at one time or the process is timing out before it finishes. Either way you just need to click the auto-fix button 6 times (one more time after each failure) for it to finish fixing all the infected files.
It would also be a good idea to run the Complete Scan again after you are done, just to make sure it got them all and they are not coming back.
For future reference, you can try the “fix as you go” method when running large scans like this one. Just click the fix button each time the scan finds a few hundred infections and the scan will keep going but it will also clean the malicious threats that it has already found, so that by the time you are done scanning you can also be nearly done cleaning. That way it won’t get hung up trying to clean thousands of infected files at once.