I did had it forget some stuff over long runs that went through several context compactions and i'd expect a larger model to be able to handle more vague instructions or have wider breadth of knowledge (if you're trying to make Qwen 3.8 27B do stuff outside the mainstream you need to provide it with some reference material to use) but i never had a problem with it not following instructions.
The harness might matter though but i'm using plain Pi (which is a very barebones harness with a very small system message) without any addons.
Would something like LMCache help here?