Even with a perfect guide, mistakes happen. Here is how to troubleshoot:
Try the sample on inside-out. Look for:
Do not go straight to fabric. Use the PDF’s instructions to draft on oak tag or manila paper. Check the following: Patternmaking For Underwear Design.pdf
Then she opened the PDF again, this time as a student, not a mourner. She flipped to Chapter One: Drafting the Basic Panty Block. Even with a perfect guide, mistakes happen
You cannot draft a pattern for a cotton jersey thong and use it for a high-compression power-mesh brief. When looking through any technical manual or PDF on the subject, the first lesson is always Even with a perfect guide