I do these on the co2, at least used to… never on my dpssl.
On the co2 my power is down around 10 or 11% and my tube is 40W… You’re probably running 50% more power than I did.
I found with too much power, it just seems to evaporate the TiO2. I don’t remember the interval I used, but it might be part of the problem.
If you are at your power minimum, then your only options are to try a larger interval and/or go faster… 
I used the material test to locate a good spot…
