Wet platforms at some light rail stations are causing mild electrical shocks to guide dogs for the blind that can cause the animals to ignore their training and make them unable to do their jobs.

The same problem surfaced eight years ago, requiring three dogs to be retrained and forcing one to retire. The dogs are given to the blind for free, but it costs more than $50,000 to train one.

The problem appeared to be solved when TriMet put capacitors along the tracks to soak up the extra voltage.

But the problem has reoccurred on the west side of the city, according to Patricia Kepler, past president of Guide Dog Users of Oregon.

Kepler said she was at a westside MAX station recently when her guide dog, Reuben, was shocked four times as they tried to board the train.

"Reuben kind of stumbled," Kepler said. "My husband asked, 'Did he just get shocked?' I said, 'No, they fixed that."'

TriMet spokeswoman Mary Fetsch said the original problem had been animals that stepped on wet train tracks. This time it appears to be when they leave the platform and step onto a train.

But transportation agency workers have not determined what's causing the jolts this time.

"We went out and did tests, and all the levels were within the safe zone," Fetsch said. "We don't know what is causing the problem at all."