Why does this happen?

What could be the possible reason for this to happen? I just oiled my machine 6 hours ago and been working since then, this is the third time this has happened today. Machine is running at around 600-650 spm (actual speed)

What could be the possible reason for this to happen? I just oiled my machine 6 hours ago and been working since then, this is the third time this has happened today. Machine is running at around 600-650 spm (actual speed)