I had similar issues with my Beltfed, but found that it was cheap magazines that were the culprit. Also working the bolt and spring back in forth and shooting it fixed the issue. PTR models have had a reputation lately for bolt gap spacing being off. I would measure it and probably send it back to PTR. While there are some bugs to be worked out I think the servicing dept has been up to par at PTR. They should fix the problem.
Call them. This COVID 19 stuff has done a number on a lot of companies. Catching them on the phone may help. I have never dealt with them but researching my next projects has given me a good bit of input. First their 9mm guns are work in progress with similar issues to what you mention. Second their PTR91 models are very well thought of and their business model is pretty solid. Third they have been receptive to their clientele regarding the issues with their 9mm models. They want to make it work but have to get through the learning curve. Of all the K models I have been researching they are the newest to the market but have a lot invested and are not a fly by night company.