S7-214 'pausing'?

Hi all
I'm encountering a problem with a new old-stock S7-214.

It's running a little sequence, and more often than not, the sequence 'freezes' in one of the states. The PLC remains in run mode. Here's the strange bit - when I click 'online', the sequence kicks off again. I'm not writing a variable, or changing ANYTHING, just going online, meaning that it's impossible to be online whilst it's in this frozen state.

One more thing - if I remain online, it runs flawlessly.

Can anyone shed any light on this?

PP

Could be a flaky memory location. Change the bit address(s) of the suspected state.
Of course, I'm only guessing at this point.

Do you have any expansion modules on this unit? I have had problems with vibrations on the older siemens 214/215's. Is the plc mounted in a high vibration location? To fix this problem we have re-seated the expansion modules. This is a short term fix, but works.