error reading from salesforce datastore to BODS

hi all,

getting this below error often while reading data from salesforce datastore to bods.

"Error reading from <Account>: <com.sforce.soap.partner.UnexpectedErrorFault: UnexpectedErrorFault>."

where Account is test table name which i am extracting from salesforce datastore.

details:

we have recently configured a datastore to read data from salesforce.

i have read the document "sbo411_ds_salesforce_en.pdf".

in the datastore i have done the setting in below snapshot to enable to read changed data from salesforce.

in the dataflow, i have the source, query transform and target table (quite a simple flow)

the job executes successfully half of the times.

but the other half of the times, i get below error

"Error reading from <Account>: <com.sforce.soap.partner.UnexpectedErrorFault: UnexpectedErrorFault>"

is there any setting change which can correct this issue?

please suggest.