James Key admits it is the "little things" that have cost Toro Rosso in this year's championship.
Toro Rosso are currently holding down sixth place in the Constructors' Championship with 45 points, three ahead of McLaren.
The team, though, had hoped for better as they previously stated that P5 was the goal for 2016.
Key, however, fears they have let themselves down by getting the little things wrong.
"There have been some frustrations," the technical director told Autosport.
"Unfortunately, it's a little bit of a thing with STR, we do all the hard work and then little things let us down or we let ourselves down.
"We are quite OK with performance but we know we are a bit compromised now with the engine, we can see we're the last in the pecking order now because everyone else has developed real quick.
"There are no big issues here, we're good as a team at the big projects.
"What we have to make sure is that we have everything covered in the finer detail in some circumstances.
"That can be what you do in an emergency in a pit stop if you have an unforeseen circumstance to a sign-off procedure for some system on the car. It's just minor things."
Key also feels that Toro Rosso need to devote more time and attention to R&D, saying a lack of resources is costing them in that department.
"There's a little bit of rebalancing in the team to do to try and get the allocation of resource a little bit better in some areas.
"We are lacking some R&D activity – which is down to resource not down to a lack of understanding – but some people are just overworked in those areas.
"So we need to try and find a way to reallocate resource to some R&D activity which will help us understand certain things better."
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