This is how the flow looks like:
And this is the error:
The flow is working perfectly most of the times, but the error happens once in a while.
I have just added a "Contains" check to the Variable, to try catch the error.
if(contains(triggerBody(),'tileValue'),div(triggerBody()['tileValue'],1000000),'20')
However the "Contains" didn't work..

I haven't changed the flow between the runs - i.e. exact same flow that first succeeds and later fails.