I own a steel hr, but this problem should affect every withings watch owner with a wirstband width of 18mm.
After less than a year, the hole I used to regulate my silicone wirstband circumference loosened (actually the "tissue" around it ripped a bit). Apparently withings silicone doesn't resist well against the metal lock.
After I changed hole by one position, that one loosened too within some months.
Now I'm using the measure immediately larger than the initial one, but I don't know for how long it will resist at this point.
Now, silicone is the most important material for watches like ours, you don't need to change the band since it's water resistant, elastic (when working out the cross-section of the arm just before the wirst can change), and comfy to sleep wearing it.
But, can you (withings) make more resistant silicone wirstband replacements? Maybe like some of the ones of 20mm width, which have a different material around each hole.