ORLANDO, Fla. -- An apparent problem with SunPass transponders at Central Florida tolls may be costing motorists cash, a Local 6 investigation found.

The report featured Barry Griffin, who tracks every penny he spends.

Griffin said when his son gave him a SunPass transponder, he created a log of every toll he'd be charged for.

"On 5.3 percent of the times I went through a toll plaza, I experienced an error," Griffin said.

The first of two errors he calculated amounted to a $1 overcharge for each transaction.

"Finally, a third time earlier this month, I got a $4 overcharge and that's what put me over the edge," Griffin said.

Griffin then called Local 6's Steven Cooper.

Cooper said an investigation found a puzzling and difficult task to reconcile his account.

On March 14, Griffin had $12.90 left in his SunPass account.

He traveled from Yeehaw Junction to Port St. Lucie -- where the toll is $3.

So, his remaining balance after the trip should have been $9.90.

However, Griffin's balance was $5.80.

"They said my balance was $5.80," Griffin said. "They charged me an additional $4.10."

Cooper reported that a $3 toll cost him $7.10.

However, on his online statement, it showed the correct points of entry and exit and the correct toll amount.

Griffin would not have noticed the error had he not been keeping track of his balance the same way he diligently balances his checkbook, Cooper reported.

Once he found the error, he couldn't get a straight answer from SunPass, according to Cooper.

"On this last incident alone, three different of their employees speculated," Griffin said. "(They) speculated three different ways about what may have happened."

Cooper called SunPass.

The agency investigated and said the when Griffin went through a toll plaza, his transponder read across two lanes at the same time.

"Do you mean that he was charged as if he went through two lanes?" Cooper asked.

"Right," said Christa Deason of the Florida's Turnpike Enterprise

"How can that happen?" Cooper said.

"Well, it could have been because the transponder was located in the wrong place," Deason said. "It could have been because his battery was going low or it could have been that there was some kind of signal interference down in that area."

SunPass said low battery issues are more common than multiple lane charges. And, there is another rare problem of someone receiving an extra charge when a car or truck follows too closely through a SunPass lane and a car is charged for having extra axles.

"I understand this is not a great deal of money but when this happens repeatedly to thousands and thousands of customers we're talking about a significant amount of money," Griffin said.

SunPass said that with two million transactions per day, its error rate is well below 1 percent -- far less than the error rate Griffin experienced.

Griffin was refunded for all the errors and he closed his account.

Anyone with problems with SunPass is urged to e-mail the Problem Solvers.

Watch Local 6 News for more on this story.