I stumbled about a problem regarding FireDAC and MSSQL 2016.

I stumbled about a problem regarding FireDAC and MSSQL 2016. The table has four fields, one being of type varbinary(max). When I omit this blob field from the SELECT, I can update any field without problems using the edit and post methods of TFDQuery. It is only when I include that blob field in the SELECT, I cannot update the other fields anymore (the blob is not changed). The post runs into a timeout. It seems that the table is somehow locked. That guess is backed by the fact that even a simple UPDATE query executed from Management Studio is also blocked until I reset my application inside the debugger.
Interestingly an INSERT runs without problems.
Has anyone encountered something similar - or even better - has a solution?