Series drift is usually blamed on the model. Look at the sheet instead. The character was described from memory at every job, and memory edits as it goes. “Dark auburn hair in a low ponytail” in frame one becomes “reddish elegant hair” by frame four, and the audience watches a stranger take her place. The repair is clerical: write her down once, on a current sheet you paste rather than retype.
Five fixed lines, always in order
Age — a number, and in this hall a mature one. Hair — colour, length and one habitual style. Build — two or three words. Face — one or two details that endure every crop. Signature — the cuff, the scar, the detail that survives any light. Everything else belongs to the changing line: outfit, corner, hour, river light. Changing lines are meant to change. Sheet lines are not.
State the lines plainly and positively; adjectives are reinterpreted at every attempt, concrete descriptions survive. And version the sheet: when she is deliberately changed, save the new text as version two with a date, so an old set can be remade exactly as it was.
Working from the sheet
Pair the sheet with changing lines that share one setting and one light, generate at the standard 6-credit cost, and keep the best third. Spend on repairs, transfers and upscales only after the cull. When a frame returns off character, the cause is almost always on the sheet: a changing line contradicted a fixed line, or a line was too vague to hold her.
What a sheet cannot do
It cannot hold a character who was never decided. Decide her on paper first. The sheet is not where the imagination happens; it is where the imagination is kept flowing, frame after frame.