I don’t know of any way of increasing airflow inside it, but where do you have it placed? For instance, if it’s in a recessed ‘cabinet’ space, it may benefit from being pulled out. If you think a sensor may be bad, have you submitted a system diagnostic within 10 minutes of experiencing this problem, and called Sonos Support to discuss it?
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.
The playbar is on an open shelf, also in the basement where it's cooler so it should be ok from that aspect.
I haven't tried Sonos support yet but will do so, since it's no longer under warranty I just wanted to see if other people experienced something similar and if it's possible to repair it.
I gave away my PLAYBARS after purchasing Arcs to replace them, but no, never had an issue with them.