It's creasing / bunching up on my back.
'Arriccia' — 'ar-RI-cha'. Three syllables. The 'cc' before 'i' = 'tch' sound. Stress on second syllable.
Describing a specific fit problem where fabric bunches or creases at the back. Technical feedback that a good tailor or fitter will immediately understand.
'Arricciarsi' = to scrunch/bunch up. 'Mi si arriccia' = impersonal reflexive meaning 'it bunches up on me'. 'Sulla schiena' = on the back. A sophisticated fit observation.
Si forma una piega dietro.
There's a fold forming at the back.
Describing the crease more technically
Il tessuto non cade bene.
The fabric doesn't fall well.
More general observation about drape
Tira sulla schiena quando mi muovo.
It pulls at the back when I move.
Describing dynamic fit problem
Italian fashion recognises that body proportions vary greatly. 'Schiena lunga' (long back) is a recognised fit category in Italian tailoring. Ready-to-wear solutions for different body proportions are increasingly available in Italian boutiques.