OK, more info:
Ticks appear for me only when remote is connected and FM radio is playing.
Ticks are noticable without doing anything in FM screen.
Higher/lower volume affects ticks volume.
Ticks do not appear on preset-select menu, main menu or context menu, unless while pressing remote/main unit buttons.
scan/preset mode, force mono and specific frequency don't affect the ticking.
Forcing higher CPU freq speeds up the ticks by the appropriate factor.
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This might be related to the new FM recording functionality, since FM mode originally was implemented without CPU interference (FM->audiomux->TLV320 bypass->headphone).