Unexpected HTTP status code '412' - appending to variable in parallel loop

[timjansenortec]

I have a logic app standard workflow that logs a lot of these exceptions:
Unexpected HTTP status code '412'.

This workflow is using a loop in parallel.
I think the exceptions are caused by updating a variable from inside this loop.

At first glance...nothing seems to go wrong in the workflow, so I assume the update of the variable is retried?
Does anybody have experience with this?
Should I be worried about all these logged exceptions?

cleaned up callstack looks like this:
[{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Storage.Http.Parsers.FastCloudTableParser.UpdateEntitiesFromResponse","level":0,"line":0},
{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Storage.FastCloudStorageTableClient+d__11.MoveNext","level":1,"line":0},
{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Storage.StorageOperationContextLogger+d__31.MoveNext","level":5,"line":0},
{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Storage.CloudStorageDataProvider+d__35.MoveNext","level":9,"line":0},
{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Storage.CloudStorageDataProvider+d__35.MoveNext","level":11,"line":0},
{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Storage.CloudStorageDataProvider+d__33.MoveNext","level":15,"line":0},
{...,"method":"Microsoft.Azure.Workflows.Worker.Jobs.VariableAppendActionJob+<UpdateVariable>d__3.MoveNext","level":19,"line":0},
{...,"method":"Microsoft.Azure.Workflows.Worker.Jobs.VariableUpdateActionJob+<TryUpdateVariable>d__12.MoveNext","level":23,"line":0},
{...,"method":"Microsoft.Azure.Workflows.Worker.Jobs.VariableUpdateActionJob+<ExecuteVariableOperation>d__8.MoveNext","level":27,"line":0},
{...,"method":"Microsoft.WindowsAzure.ResourceStack.Common.Algorithms.AsyncRetry+d__31.MoveNext","level":31,"line":0}, {...,"method":"Microsoft.Azure.Workflows.Worker.Jobs.VariableUpdateActionJob+<ExecuteAction>d__7.MoveNext","level":35,"line":0}, {...,"method":"Microsoft.Azure.Workflows.WebJobs.Engines.FunctionActionExecutionEngine+<ExecuteEdgeActionCallback>d__3.MoveNext","level":39,"line":0}, {...,"method":"Microsoft.Azure.Workflows.WebJobs.Extensions.Trigger.WorkflowRuntimeTriggerProcessor+<HandleFlowTrigger>d__0.MoveNext","level":43,"line":0}, {...,"method":"Microsoft.Azure.WebJobs.Host.Executors.VoidTaskMethodInvoker2+d__2.MoveNext","level":48,"line":20,"fileName":"C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\VoidTaskMethodInvoker.cs"},
{...,"method":"Microsoft.Azure.WebJobs.Script.Description.DotNetFunctionInvoker+MethodInvoker2+<InvokeAsync>d__2.MoveNext","level":53,"line":534,"fileName":"/_/src/WebJobs.Script/Description/DotNet/DotNetFunctionInvoker.cs"}, {...,"method":"Microsoft.Azure.WebJobs.Script.Description.DotNetFunctionInvoker+<InvokeCore>d__26.MoveNext","level":58,"line":273,"fileName":"/_/src/WebJobs.Script/Description/DotNet/DotNetFunctionInvoker.cs"}, {...,"method":"Microsoft.Azure.WebJobs.Script.Description.FunctionInvokerBase+<Invoke>d__24.MoveNext","level":63,"line":82,"fileName":"/_/src/WebJobs.Script/Description/FunctionInvokerBase.cs"}, {...,"method":"Microsoft.Azure.WebJobs.Host.Executors.VoidTaskMethodInvoker2+d__2.MoveNext","level":68,"line":20,"fileName":"C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\VoidTaskMethodInvoker.cs"},
{...,"method":"Microsoft.Azure.WebJobs.Host.Executors.FunctionInvoker`2+d__10.MoveNext","level":73,"line":52,"fileName":"C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionInvoker.cs"},
{...,"method":"Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+d__33.MoveNext","level":78,"line":581,"fileName":"C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs"},
{...,"method":"Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+d__32.MoveNext","level":83,"line":527,"fileName":"C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs"},
{...,"method":"Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor+d__26.MoveNext","level":88,"line":306,"fileName":"C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Executors\FunctionExecutor.cs"}]

[timjansenortec]

I did some further checking myself:

made a workflow that initializes an array variable with values 1-20
then copied each value in this array to another array variable in a parallel loop
then checked the values in the copied array variable
this indeed reproduces the exception: Unexpected HTTP status code '412'

the copied variable shows a different order of the values...which is to be expected, but no values are lost
[  2,  5,  1,  9,  8,  14,  13,  17,  18,  16,  4,  6,  11,  19,  20,  7,  10,  15,  3,  12]

based on this small test, I think these exceptions are not a problem.