I’m not seeing the issue, but have you tried rebooting the speakers post update and retuning the room? If so, and the problem persists with either Trueplay on/off, then maybe try unbonding/rebonding the surrounds and Trueplay tuning again.
As a final suggestion, adjust the ‘TV Level’ slider control over to the left in the Arc ‘room’ surround audio settings.
Still no joy, then after playing audio where you notice the issue, within 20 minutes of the issue occurring, submit a Sonos diagnostic report from the ‘Settings/Support’ area of the Sonos App. Make a note of the reference generated, and when practicable, contact/chat to Sonos Support Staff about the matter via this LINK and see what they can suggest to resolve the matter.