The NFL’s negotiations with the NFL Referees Association on a new collective bargaining agreement are not in a good place, sources told ESPN’s Adam Schefter.

The league held committee meetings last week in Palm Beach, Florida, where owners were updated on the status of the talks on a deal to replace the expiring CBA, sources told Schefter.

One source told Schefter that “frustration is mounting” among owners.

The NFL said last year in a memo that it “remained focused on implementing changes to the agreement in ways that will improve the performance of our game officials, increase accountability, and ensure that the highest-performing officials are officiating our highest profile games.”

The referees’ union, however, wants to preserve the status quo or, in some cases, roll back the league’s access to working with game officials.

The league’s current CBA with the NFLRA expires at the end of May. The last officiating lockout was in 2012 and lasted 110 days, ending after three weeks of controversial calls by replacement officials.

Scott Green, the NFLRA executive director, told ESPN in December that the union looked forward to negotiating a new deal but declined to offer specifics, saying it was “not really helpful to do it by way of the media at this point.”