It is an expected behavior that the Beoplay A6 reduces its output volume level when getting too hot inside the electronics or speaker drivers; there is an automatic temperature protection circuit built-in to protect the product.

The protection circuit depends on:
1. volume step / level, music type (bass levels) and time played at specific high volume level.
2. ambient temperature

The product will protect itself from getting too hot inside and will reduce the volume level automatically to reduce the temperature in the electronics  - if necessary, it will even shut down. Once the Beoplay A6 has cooled down, a mains reset must be done, and it is possible to play again.

if its doing often, i would send it in if its under warranty, I have seen some have Been change on defekt circuit sensor..

/forum/imported-unmapped/beoplay-a6-volume-neemt-af

I'm facing the exact same problem. 

Resetting, updating to newest version of software - nothing helps.

Same problem exists independantly whether the source is moblie (via Bluetooth, Spotify Connect, Chrome Cast), PC (via Bluetooth)

Quite desparate about this.

Claus

Unfortunately I can not use my A6 for several months now...still haven't find the solution. I asked Beo service...they recomended buying a new electric panel for 1000 Eur ....hahaha