Here you go.

This is from a different app server and database, however the issue is the same

Got the query plan:

Showplan XML<ShowPlanXML xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan" Version="1.1" Build="10.50.2500.0"><BatchSequence><Batch><Statements><StmtSimple><QueryPlan CachedPlanSize="112" CompileTime="10" CompileCPU="10" CompileMemory="752"><RelOp NodeId="2" PhysicalOp="Table Merge" LogicalOp="Merge" EstimateRows="1" EstimateIO="0.05" EstimateCPU="5e-006" AvgRowSize="11" EstimatedTotalSubtreeCost="0.0736757" Parallel="0" EstimateRebinds="0" EstimateRewinds="0"><OutputList><ColumnReference Database="[sms_smsgw3]" Schema="[dbo]" Table="[sent]" Alias="[target]" Column="se_ref"/></OutputList><Update DMLRequestSort="0"><Object...

Unfortunately I cannot get the actual execution plan.

I have spoken to the dev's and they will be looking to add a "lock" to the secondary threads.

We will then include a...