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