Replaced front assembly, now sleep/wake button erratic?

This has happened to me twice so far, and I'm not sure what the issue is. I replaced the front assembly on these ipod touch 4th gens, and now the sleep buttons are not working right.

The first one's sleep button will not respond at all, while the rest of the ipod, including the volume rocker, work perfectly.

The second one, the ipod functions completely, except the sleep button is erratic. whenever it turns on or wakes up, it shows the "slide to power off" button and if I turn the ipod off, it will turn itself back on without me pressing anything.

Am I doing something wrong with the repair? I have done others that worked out perfectly, just these two have problems.