5320 Offhook with handset button not lifting enough

[CMHTech]

I have a few phones that are exhibiting the same problems lately and wondered if anyone had a fix for this. When lifting the handset the button doesn't lift enough to get dial tone or answer a call. I've taken several of these apart and cleaned, checked the wire spring and reassembled and they appear to work for a short while. I can test pick up on the handset dozens of times and they work, but it isn't long after putting them back in service that I see the problem again. Is there a replacement spring I can buy, or a better way to clean these? This is a hospital environment so it's not dusty and dirty.

Thanks for any advice!

[JasonTL]

I have had the exact opposite issues lately. A couple phones that you can answer the call, but then not hang the phone up? I replaced 2 phones with brand new phones and still had the same issue. Mitel is looking into it.