Wells Fargo & Co.’s disclosure that it may have pushed thousands of car buyers into loan defaults and repossessions by charging them for unwanted insurance is raising doubts about the bank’s ability to put proper controls in place.

“The steady drip of revelations is concerning as it makes quantifying and qualifying the extent of the internal control failures difficult,” Isaac Boltansky, an analyst at Compass Point Research & Trading, said Friday in an email. “Which is worrisome for both Washington and Wall Street.”