Series drift is usually blamed on the model. Look at the sheet instead. The character was described from memory at every job, and memory takes a fresh order each time it is asked. “Dark blonde hair in a low side twist” in frame one becomes “blonde elegant hair” by frame four, and the audience watches a stranger take her place. The repair is clerical: write her once, on a triple sheet you paste rather than retype.
Five fixed lines, always in order
Age — a number, and at this desk a mature one. Hair — colour, length and one habitual style. Build — two or three words, no more. Face — one or two details that survive any light. Signature — the one object or mark that identifies her at a glance.
The sheet stays on the desk
Every bench works with the sheet in sight, and every dispute between frames is settled by reading it aloud. It is a small courtesy with a large effect: nobody — human or model — improvises a character who has already been written down.