Pinephone keyboard poor pogo pin connection

[jurop88]

Unless the shim can pass directly under the the connectors (which doesn't seem possible)

I take no responsibility for that but... i'd say it is possible. I tried different shims cut off from plastic boxes recycled from plastic littery (some biscuits container, an olive container, yogurt box and so on...)
A 0.7mm thick shim made the back bulgy, a 0.15mm was too thin. In the end I cut a plastic rectangle of approx 16x10mm 0.37mm thick and managed to entirely slide it between the contacts and the back of the case using some 'plastic case openers' (the blue triangles from iFixit set). It is totally invisible and in my case it made the contacts fully reliable.