Personally I think "Timelash" epitomises what went wrong with Peri, in that it's an otherwise generic "Doctor overthrows oppressive government on alien planet" story that begins with Peri being threatened with having acid squirted in her face, ends by having her threatened with mutation followed by a life of rape and forced pregnancy, and spends the remaining portion with her spending most of her time manacled and being threatened with torture by everyone in sight, including the alleged local good guys.

The "extended TARDIS scene" actually redeems it for me, in that it's one of the few moments in S22 where it appears that the Doctor actually does give a toss about Peri.