A trigger returned a resultset and/or was running with SET NOCOUNT OFF while another outstanding result set was active

Question

I have 2 servers connected over a low speed wan and we're running SQL Server 2008 with Merge replication.
At the subscriber, sometimes when attempting to insert new rows, I get this error:
A trigger returned a resultset and/or was running with SET NOCOUNT OFF while another outstanding result set was active.
My database doesn't have any triggers; the only triggers are the one created by the Merge replication
Also, whenever this error occurs it automatically rolls back the existing transaction
I am using DataTables and TableAdapters to
insert and update the database using transactions
What I have checked:
the database log file size is below 50Mb
Checked the source code for Zombie transactions (since I wasn't able to retrieve the actual error at the beginning)
Checked the connection between the two servers and found it congested
Questions:
How to avoid this behavior and why it's occurring at first place?
Why it's cancelling the open transaction?

Answer 1

did the issue happen on some specific tables or all the tables?
I suggest to run sql server trace at publisher and subscriber when the issue happens. Please involve below events and columns
Stored      Procedures
RPC:Completed      
RPC:Starting
sp:Completed
sp:Starting
sp:StmtStarting      
sp:StmtCompleted      
TSQL
SQL:StmtCompleted
SQL:StmtStarting      
SQL:BatchCompleted
SQL:BatchStarting      
Unprepare SQL
 ‘Errors and Warnings’
ErrorLog
EventLog
Exceptoin
attention
columns:
 TextData ,error, LoginName, ApplicationName , StartTime ,EndTime,DatabaseName,NestLevel,ObjectName,ObjectType,ServerName,eventsequence,linenumber,cpu,reads ,writes,rowcounts,clientprocessid,spid,transactionid
Once the issue happens, please check the trace to find which step or statement hit the error.