The "lasts forever" claims from some shops are honestly a bit much, quality film with proper installation should last several years but nothing lasts truly forever with daily exposure. Worth being a little skeptical of shops making those kinds of absolute claims.
Had a similar rough shift pattern on my A6 last summer. Turned out to be a mechatronic temperature sensor giving bad readings under load. Specialist found it in one session, dealer had quoted a full fluid service first without even checking that component.
We standardized on a similar sized crate about 8 months ago for mixed cold storage use. No warping issues, dimensions have stayed consistent even with daily handling. One thing worth checking though is how the crates perform going in and out of temperature zones repeatedly, that transition seems...