I will fail 1 (or 2) classes this semester as a master's student. Should I forget about PhD applications to schools in US? I am an engineering master's student, and I could not cope with the quarantine during the last few months, and I will be failing one or two classes this semester.
I just finished my year, and I had a very high GPA in my first semester. Is this red flag a dealbreaker for PhD applications in the US? I am not sure if I should bother applying.
I also had this unusual situation where I was about to transfer credit from a former university where I was a graduate student but received no degree, and it was too late to drop by the time my grades were transferred, because quarantine caused delay when I was obtaining documents. So hopefully I will have completed a decent portion of my credits, but realistically I am not hopeful.
If getting a PhD is something you really want to do, I suggest applying. If your failing those classes is truly not a reflection of your abilities or motivation, but - as you said - relating to effects of the pandemic/quarantine, then hopefully the rest of your course grades and other application materials will make up for those two failed courses.
When I applied to PhD programs, my own bit of insecurity came from the fact that I had graduate credits from another university where I didn't receive a degree (it was my first attempt at a PhD and it just wasn't a good fit). I decided to address it in my personal statement. I acknowledged that I attempted my PhD before but quit, explained why, and quickly moved on to explain how it was still a learning experience for me in terms of coursework, gaining teaching experience,and learning more about myself and what I valued/prioritized in a PhD program.
I would suggest you do something similar in your personal statement (if engineering programs require them), and to keep it brief. Acknowledge the failed courses, offer an explanation for why you failed the classes in such a way that they understand that this was an atypical experience for you, and then come back with a statement of some sort that illustrates why - despite what you just shared - you're still a great candidate for their program. None of this should dominate the personal statement, I would keep it to just a few sentences.