NetVanta 1534P keeps disconnecting devices

[thunter]

I have a NetVanta 1534P, I have 2 other switches plugged into this main switch plus a view devices plugged in directly to the switch itself. The 2 switches that are plugged  in each have about 10 devices plugged in and all are working fine with no interruptions. However, the 6 devices plugged directly into the main switch keep randomly disconnecting, sometimes its every 15 minutes, sometimes it is an hour or so. Any ideas why those devices would loose connection and the 2 other switches do not? Thank you.

[thunter]

Here are the errors in the log:

POWER_OVER_ETHERNET.giga-swx 0/4 Couldn't enable pre-802.3at mode! --err code -3

POWER_OVER_ETHERNET The PoE subsystem has detected an error and will be internally reset.