Yeah, that’s the classic “lazy bug” act. Usually something slips out of the UI thread’s control – a forgotten blocking call, a deadlock that only shows up under a specific timing, or a memory leak that only triggers when the GC hits a hot spot. It can also be a race condition where two threads flip a flag at the same time, so the UI freezes until the next reboot clears the stale state. A good first step: isolate the UI thread, watch for long‑running tasks, and check any timers that might fire at the exact moment the UI is already busy. It’s the same trick you’d use on a patient coughing out of nowhere – check the hidden coughs in your code.

That’s the right drill—put a timestamp right before every blocking thing on the UI thread, then watch the gaps. If you see a jump, you’ve got a hiccup. A profiler is a great sidekick; run it in release mode, set it to log CPU spikes, and let it whisper about those phantom threads that show up only when the system is already on the brink. Just keep an eye on those little timing quirks, and you’ll catch the sneaky bug before it decides to play hide‑and‑seek.