Oh my yes! Same issues, but these go back a couple of years. I picked a seat during the reservation process through United only to find that seat assignment kept disappearing from my trips. It was only when I took the Lufthansa record locator from my UAL reservation and created an account on Lufthansa, paid for the seat (funny, they don't mention that on UAL) that the seat assignment stuck around long enough for us to take the flight. I then called Lufthansa to confirm the seat assignments were solid.
Endless holds with Lufthansa, tried the toll free and the "in Germany number." LH App would weirdly disappear all-together from my phone, most recently last August when we were connecting in FRA and our boarding passes were ready to scan - poof! What a pain!
True story, we flew Lufthansa from Athens to FRA in 2022. Flight was delayed due to airline issues (not weather) meaning we were stuck in FRA overnight and we were entitled to the Euro fine where airlines pay passengers something like 800EUR for delays over three hours. I was given the penalty form at FRA, filled it out the day we got home. Ignored by Lufthansa for months. It was only when I reached out to the New York Times travel help that - miraculously - we got about $1800 within hours.
We are UAL customers, so will be flying Lufthansa again, but agree - they need to upgrade the traveler experience.