I had this issue with my remote, and just repaired it. Unfortunately I forgot to take pictures.
My problematic directional keys were not clicking (felt stuck). I removed the clickpad following the Siri remote disassembly instructions, and when inspecting it, noticed that these keys had pads of "tape" above them. I carefully lifted this pad, and the key is essentially the two terminals on the PCB, with a flexible metal dish on top, which is kept in place by the tape. This dish is what "clicks" and closes the contact.
On my two defective keys, there was some oxidation on the terminals and the dish, both greenish copper oxide, and reddish iron oxide (I guess). I cleaned these up with isopropyl alcohol and rubbed the oxidized part of the dish with a needle (since just isopropyl was not doing the job). I then reattached these dishes back on top of the keys, and added bits of electrical tape to hold the sides I lifted in place.
If you take care to only lift one side of the assembly, it's easier to reassemble because the alignment will be preserved.
Let me know if this helps, and if you take any pictures of the disassembly, we could post the instructions (I can refine the text).