 Problem 1\underline{\textit{\textbf{ has to do with the fact that even among the 500 Hz data, the inter-timestamp intervals varied widely.
<fluency>  Problem 1\underline{\textit{\textbf{ has to do with the fact that even among the 500 Hz data, the inter-timestamp intervals varied widely.
 Problem 1\underline{\textit{\textbf{ has to do with the fact that even among the 500Hz data, the inter-timestamp intervals varied widely.