Mass data upload to SAP ByD - Locking object not possible; object locked by _

Hello Smartbear suppor team! 

I am working at a company where SOAP UI is used for certain mass updates in SAP Business By Design. We are having huge struggles with updating one certain field for more than 200-500 items.

The messages we receive in SOAP UI are the following: 

Tab XML: 

<TypeID>101(/AP_ESI_COMMON/)</TypeID>
<CategoryCode>FOL.FOL</CategoryCode>
<SeverityCode>3</SeverityCode>
<Note>Locking object not possible; object locked by _MANAGEMATER (_MANAGEMATER)</Note>

Tab RAW: 

HTTP/1.1 200 OK

When we receive these errors, in certain cases the data is updaded in the system, in certain cases the data is not actually updated in the system. 

Could you please advice if there is any setting that we can change in SOAP UI to improve this? Please take in consideration that the Socket Timeout needed to be raised to 600 000 ms in order to overcome the missing raw data and actually run the file for upload fully. 

Many thanks in advance! 
Ekaterina