Siemens Mobile panels 'freeze'

I have 4 mobile panels 177 on a Profibus network, and somtimes a panel (not always the same) freezes (no manipulation is possible anymore).
In the software of the panel I have one tag that sees an integer variable in the plc that is raised with value one each scan cycle of the plc, this tag has an update time of 500 ms cyclic continuous.
This tag has an event on change of value that is transfers its own value to another tag.
This last tag has an update time of 500 ms cyclic continuous and the plc looks at this tag to see if the panel is connected (this is an alternative for the live bit of the panel, that I didn't wanted to use).
Could this be a reason for the freezing of the panel (no manipulations possible anymore)?
Or could there be other reasons?
As an alternative I tried to use the life bit of the coordination word from the area pointer of the panel.
This worked ok for one panel, but if I connect more then one panel I get a system message on the panel on startup : 'Interference on the bus'.
The area pointer for coordination for each panel in the cpu are in different databloks for each panel.
Why doesn't this work for more then one panel on the bus??????

Are the bus parameters calculated correctly ?
Do you have all 4 panels integrated in the same STEP7 project, and every other Profibus node as well ?

JesperMP said:

Are the bus parameters calculated correctly ?
Do you have all 4 panels integrated in the same STEP7 project, and every other Profibus node as well ?

Click to expand...

All 4 panels are integrated in the same S7-project (just as every node).
But I did not download the plc hardware since I added the panels.
Do you have experience with this kind of problem?
Since it are mobile panels, none of them can be connected, or all 4.

The TTR downloaded to all stations must be calculated by including all stations.

I have not experienced, but heard of panels behaving erratically when there are bus problems.

JesperMP said:

The TTR downloaded to all stations must be calculated by including all stations.

I have not experienced, but heard of panels behaving erratically when there are bus problems.

Click to expand...

Does each panel introduce an extra master on the Profibus?

My profibus adresses for the panels are 26,27,28,29.
May they be consecutive?

Plc_User said:

Does each panel introduce an extra master on the Profibus?

Click to expand...

Yes.

Plc_User said:

My profibus adresses for the panels are 26,27,28,29.
May they be consecutive?

Click to expand...

Yes.

To come back on my second question :
///As an alternative I tried to use the life bit of the coordination word from the area pointer of the panel.
This worked ok for one panel, but if I connect more then one panel I get a system message on the panel on startup : 'Interference on the bus'.
The area pointer for coordination for each panel in the cpu are in different databloks for each panel.
Why doesn't this work for more then one panel on the bus??????
/////

Does anyone know how you set up the coordination area in multiple panels on a profibus network with one cpu?

Thanks