Thanks for the clear steps. Unsynced lyrics should return to the top when the song changes. I found the missing reset in the version you’re using; my development version already includes that reset, although it hasn’t been published yet.
I found your 15.0.1 logs, but they don’t show what causes the separate progress-bar freeze. Please update to 15.1.0 and try reproducing that again. Read the appropriate announcement in the changelog for the official APK instructions if Google Play hasn’t approved that release yet.
If the progress bar freezes again, please enable debug mode before starting the sequence, reproduce it, then disable debug mode and upload the logs promptly using this guide. Reply with the app version, upload description and occurrence time so I can find the right recording.