Pop superstar Taylor Swift said on Friday it was “excruciating” for her to watch fans struggle to secure tickets for her upcoming U.S. tour after she had been assured that Ticketmaster (LYV.N) could handle large demand.

Many people hoping to land seats at Swift’s first tour in five years said they waited hours and were repeatedly kicked off the Ticketmaster website during presales this week.

Swift posted on Instagram that it was “excruciating for me to just watch mistakes happen with no recourse.”

She said she was “not going to make excuses for anyone” because her team had been assured by ticket sellers that they could handle a surge in demand. Ticketmaster offered seats for most shows on the 20-city, 52-date U.S. stadium tour. SeatGeek sold tickets for a handful of performances in Texas and Arizona and also reported long waits.

Ticketmaster has said it experienced unprecedented interest in Swift’s tour and worked quickly to resolve technical problems. The company did not immediately respond to a request for comment on Friday.

Swift said it was “truly amazing” that 2.4 million people got tickets, “but it really pisses me off that a lot of them feel like they went through several bear attacks to get them.”

The “Anti-Hero” singer-songwriter said she was “trying to figure out how this situation can be improved in the future.”