Pulsing/ Chaser Emissive Material

Good evening and thank you for the quick and easy solution.
I have replicated this method this afternoon with success. However the project crashed and the material was apparently ghosted (there in the preview, but the file nowhere to be seen later).
And when I have tried to replicate it again, the Time node seems to be doing some really, really weird sh*t… Such as dipping under 0.
Any clue on what could have happend?