Your most disappointing purchase or audition?

I've had a few.

bought a Naim Nait 3. Loved it in the store. Returned it within a week- way forward at home

Brought home some CJ preamp to audition perhaps 22 years ago. Noisy as anything and a turn off transient destroyed a tweeter (though years later i bought a CJ 17LS2 which I thought was the finest preamp I ever heard in my home)

Auditioned a VPI table (HW19) in a store- the store just could not get the belt to stay on. Bought a Rega instead. This was in perhaps 1990.

Fortunately, I never really experienced buyers remorse say 6 months or more after settling on a piece of gear.

Finally, there have been too many speakers that got stellar write ups which I just didn't care for.
My biggest disappointments were: B&W 802s3, Naim Nait 5i, Magnepan 1.7, PAD interconnects (don't remember the model, price was about $1000-1500), PS Audio PCA-2, Musical Fidelity A3.5, Pass X2.5, Clements RT-7
Rogue Sphinx integrated. Had crackling coming from the left channel and right channel would cut out completely when changing inputs. Sent it back to Rogue for repair. Rogue never contacted me to give me status of the repair. Never returned my messages..(four). The fifth time I call they give it a "clean bill of health". Sold it while it was at Rogue. Rogue ships it to the buyer and he had EXACTLY THE SAME ISSUES. Disappointed with the integrated, the company, everything.
great question/thread

Had an NAD 375 BEE, loved its sound paired with PSB then Dynaudio speakers, but fell into upgrade bug and reading about NAD being "mid-fi".

So, sold it here for a Musical Fidelity A5. Wow, did my my speakers shut down. Terrible, closed in, dead.

Sold it for my current Krell 400xi, and loving the sound.

...but, still have the upgrade bug. Crap.