IMZ220 goes slow and noise

Hi,

 

  I've a solution running with Android and 10 IMZ220 printers in ZPL mode since a year. It was working fine, but since a week 4 or 5 of the printers starts to print slow and very loud noise ·of machine "grgrgrgrgrgrgr".

It makes a burned label, after a time the printer starts to work fine.

If I disconect my app and press the feed button the problem is the same, the feed is very noisy and slow.

 

Please could you tell me if this is a problem with the printers? it has a life cycle? Because the problem has started with very few days of difference between units...

 

Best regards,

thanks a lot.